Main.cc: In function ‘int main()’:
Main.cc:40:5: error: ‘cout’ was not declared in this scope
cout(tong(a,n,k));
^~~~
Main.cc:32:10: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
scanf("%d",&n);
~~~~~^~~~~~~~~
Main.cc:34:10: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
scanf("%d",&k);
~~~~~^~~~~~~~~
Main.cc:37:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
scanf("%d",&a[i]);
~~~~~^~~~~~~~~~~~