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Main.cc: In function ‘int main()’: Main.cc:10:9: error: no match for ‘operator>>’ (operand types are ‘std::ostream {aka std::basic_ostream}’ and ‘int’) cout>>a*x + b*y; ~~~~^~~~~~~~~~~ Main.cc:10:9: note: candidate: operator>>(int, int) Main.cc:10:9: note: no known conversion for argument 1 from ‘std::ostream {aka std::basic_ostream}’ to ‘int’ In file included from /usr/include/c++/7/string:53:0, from /usr/include/c++/7/bits/locale_classes.h:40, from /usr/include/c++/7/bits/ios_base.h:41, from /usr/include/c++/7/ios:42, from /usr/include/c++/7/istream:38, from /usr/include/c++/7/sstream:38, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/bits/basic_string.tcc:1465:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) operator>>(basic_istream<_CharT, _Traits>& __in, ^~~~~~~~ /usr/include/c++/7/bits/basic_string.tcc:1465:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/istream:991:0, from /usr/include/c++/7/sstream:38, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/bits/istream.tcc:963:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT2*) operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s) ^~~~~~~~ /usr/include/c++/7/bits/istream.tcc:963:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/istream:991:0, from /usr/include/c++/7/sstream:38, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/bits/istream.tcc:931:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&) operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c) ^~~~~~~~ /usr/include/c++/7/bits/istream.tcc:931:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/sstream:38:0, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/istream:756:5: note: candidate: template std::basic_istream& std::operator>>(std::basic_istream&, unsigned char&) operator>>(basic_istream& __in, unsigned char& __c) ^~~~~~~~ /usr/include/c++/7/istream:756:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/sstream:38:0, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/istream:761:5: note: candidate: template std::basic_istream& std::operator>>(std::basic_istream&, signed char&) operator>>(basic_istream& __in, signed char& __c) ^~~~~~~~ /usr/include/c++/7/istream:761:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/sstream:38:0, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/istream:803:5: note: candidate: template std::basic_istream& std::operator>>(std::basic_istream&, unsigned char*) operator>>(basic_istream& __in, unsigned char* __s) ^~~~~~~~ /usr/include/c++/7/istream:803:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/sstream:38:0, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/istream:808:5: note: candidate: template std::basic_istream& std::operator>>(std::basic_istream&, signed char*) operator>>(basic_istream& __in, signed char* __s) ^~~~~~~~ /usr/include/c++/7/istream:808:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/sstream:38:0, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/istream:980:5: note: candidate: template typename std::enable_if >, std::__is_convertible_to_basic_istream<_Istream>, std::__is_extractable::__istream_type, _Tp&&, void> >::value, typename std::__is_convertible_to_basic_istream<_Tp>::__istream_type>::type std::operator>>(_Istream&&, _Tp&&) operator>>(_Istream&& __is, _Tp&& __x) ^~~~~~~~ /usr/include/c++/7/istream:980:5: note: template argument deduction/substitution failed: /usr/include/c++/7/istream: In substitution of ‘template typename std::enable_if >, std::__is_convertible_to_basic_istream<_Istream>, std::__is_extractable::__istream_type, _Tp&&, void> >::value, typename std::__is_convertible_to_basic_istream<_Tp>::__istream_type>::type std::operator>>(_Istream&&, _Tp&&) [with _Istream = std::basic_ostream&; _Tp = int]’: Main.cc:10:19: required from here /usr/include/c++/7/istream:980:5: error: no type named ‘type’ in ‘struct std::enable_if’ In file included from /usr/include/c++/7/ccomplex:39:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/complex:493:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::complex<_Tp>&) operator>>(basic_istream<_CharT, _Traits>& __is, complex<_Tp>& __x) ^~~~~~~~ /usr/include/c++/7/complex:493:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:66:0, from Main.cc:1: /usr/include/c++/7/bitset:1462:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::bitset<_Nb>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, bitset<_Nb>& __x) ^~~~~~~~ /usr/include/c++/7/bitset:1462:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:72:0, from Main.cc:1: /usr/include/c++/7/iomanip:71:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Resetiosflags) operator>>(basic_istream<_CharT, _Traits>& __is, _Resetiosflags __f) ^~~~~~~~ /usr/include/c++/7/iomanip:71:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:72:0, from Main.cc:1: /usr/include/c++/7/iomanip:101:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setiosflags) operator>>(basic_istream<_CharT, _Traits>& __is, _Setiosflags __f) ^~~~~~~~ /usr/include/c++/7/iomanip:101:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:72:0, from Main.cc:1: /usr/include/c++/7/iomanip:132:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setbase) operator>>(basic_istream<_CharT, _Traits>& __is, _Setbase __f) ^~~~~~~~ /usr/include/c++/7/iomanip:132:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:72:0, from Main.cc:1: /usr/include/c++/7/iomanip:170:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setfill<_CharT>) operator>>(basic_istream<_CharT, _Traits>& __is, _Setfill<_CharT> __f) ^~~~~~~~ /usr/include/c++/7/iomanip:170:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:72:0, from Main.cc:1: /usr/include/c++/7/iomanip:200:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setprecision) operator>>(basic_istream<_CharT, _Traits>& __is, _Setprecision __f) ^~~~~~~~ /usr/include/c++/7/iomanip:200:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:72:0, from Main.cc:1: /usr/include/c++/7/iomanip:230:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setw) operator>>(basic_istream<_CharT, _Traits>& __is, _Setw __f) ^~~~~~~~ /usr/include/c++/7/iomanip:230:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:72:0, from Main.cc:1: /usr/include/c++/7/iomanip:264:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Get_money<_MoneyT>) operator>>(basic_istream<_CharT, _Traits>& __is, _Get_money<_MoneyT> __f) ^~~~~~~~ /usr/include/c++/7/iomanip:264:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:72:0, from Main.cc:1: /usr/include/c++/7/iomanip:418:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Get_time<_CharT>) operator>>(basic_istream<_CharT, _Traits>& __is, _Get_time<_CharT> __f) ^~~~~~~~ /usr/include/c++/7/iomanip:418:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from Main.cc:1: /usr/include/c++/7/bits/valarray_after.h:411:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator>>(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::_Expr<_Dom2, typename _Dom2::value_type>&) _DEFINE_EXPR_BINARY_OPERATOR(>>, __shift_right) ^ /usr/include/c++/7/bits/valarray_after.h:411:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘const std::_Expr<_Dom1, typename _Dom1::value_type>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from Main.cc:1: /usr/include/c++/7/bits/valarray_after.h:411:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator>>(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&) _DEFINE_EXPR_BINARY_OPERATOR(>>, __shift_right) ^ /usr/include/c++/7/bits/valarray_after.h:411:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘const std::_Expr<_Dom1, typename _Dom1::value_type>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from Main.cc:1: /usr/include/c++/7/bits/valarray_after.h:411:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator>>(const typename _Dom::value_type&, const std::_Expr<_Dom1, typename _Dom1::value_type>&) _DEFINE_EXPR_BINARY_OPERATOR(>>, __shift_right) ^ /usr/include/c++/7/bits/valarray_after.h:411:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: mismatched types ‘const std::_Expr<_Dom1, typename _Dom1::value_type>’ and ‘int’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from Main.cc:1: /usr/include/c++/7/bits/valarray_after.h:411:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator>>(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::valarray&) _DEFINE_EXPR_BINARY_OPERATOR(>>, __shift_right) ^ /usr/include/c++/7/bits/valarray_after.h:411:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘const std::_Expr<_Dom1, typename _Dom1::value_type>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from Main.cc:1: /usr/include/c++/7/bits/valarray_after.h:411:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator>>(const std::valarray&, const std::_Expr<_Dom1, typename _Dom1::value_type>&) _DEFINE_EXPR_BINARY_OPERATOR(>>, __shift_right) ^ /usr/include/c++/7/bits/valarray_after.h:411:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: mismatched types ‘const std::_Expr<_Dom1, typename _Dom1::value_type>’ and ‘int’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0, from Main.cc:1: /usr/include/c++/7/valarray:1181:1: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator>>(const std::valarray<_Tp>&, const std::valarray<_Tp>&) _DEFINE_BINARY_OPERATOR(>>, __shift_right) ^ /usr/include/c++/7/valarray:1181:1: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘const std::valarray<_Tp>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0, from Main.cc:1: /usr/include/c++/7/valarray:1181:1: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator>>(const std::valarray<_Tp>&, const _Tp&) _DEFINE_BINARY_OPERATOR(>>, __shift_right) ^ /usr/include/c++/7/valarray:1181:1: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘const std::valarray<_Tp>’ cout>>a*x + b*y; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0, from Main.cc:1: /usr/include/c++/7/valarray:1181:1: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator>>(const _Tp&, const std::valarray<_Tp>&) _DEFINE_BINARY_OPERATOR(>>, __shift_right) ^ /usr/include/c++/7/valarray:1181:1: note: template argument deduction/substitution failed: Main.cc:10:19: note: mismatched types ‘const std::valarray<_Tp>’ and ‘int’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:505:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::mersenne_twister_engine<_UIntType, __w, __n, __m, __r, __a, __u, __d, __s, __b, __t, __c, __l, __f>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:505:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:898:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::uniform_int_distribution<_IntType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:898:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:960:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::uniform_real_distribution<_IntType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:960:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:2147:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::cauchy_distribution<_RealType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:2147:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:49:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.h:3644:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::bernoulli_distribution&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.h:3644:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:1925:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::normal_distribution<_RealType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:1925:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:1104:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::geometric_distribution<_IntType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:1104:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:2469:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::gamma_distribution<_RealType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:2469:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:1754:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::exponential_distribution<_RealType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:1754:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:2546:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::weibull_distribution<_RealType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:2546:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’ cout>>a*x + b*y; ^ In file included from /usr/include/c++/7/random:51:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:108, from Main.cc:1: /usr/include/c++/7/bits/random.tcc:2622:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::extreme_value_distribution<_RealType>&) operator>>(std::basic_istream<_CharT, _Traits>& __is, ^~~~~~~~ /usr/include/c++/7/bits/random.tcc:2622:5: note: template argument deduction/substitution failed: Main.cc:10:19: note: ‘std::ostream {aka std::basic_ostream}’ is not derived from ‘std::basic_istream<_CharT, _Traits>’