Mã chấm: 281966

Main.cc: In function ‘int main()’:
Main.cc:4:5: error: ‘cin’ was not declared in this scope; did you mean ‘std::cin’?
    4 |     cin >> A >> B >> X >> Y;
      |     ^~~
      |     std::cin
In file included from Main.cc:1:
/usr/include/c++/11/iostream:60:18: note: ‘std::cin’ declared here
   60 |   extern istream cin;           /// Linked to standard input
      |                  ^~~
Main.cc:5:5: error: ‘cout’ was not declared in this scope; did you mean ‘std::cout’?
    5 |     cout << A*X+B*Y;
      |     ^~~~
      |     std::cout
In file included from Main.cc:1:
/usr/include/c++/11/iostream:61:18: note: ‘std::cout’ declared here
   61 |   extern ostream cout;          /// Linked to standard output
      |                  ^~~~