/in/foo.cc: In function 'int main()':
/in/foo.cc:6:2: error: 'cin' was not declared in this scope
  cin>>n;
  ^~~
/in/foo.cc:10:5: error: 'cout' was not declared in this scope
     cout<<"YES"<<endl;
     ^~~~
/in/foo.cc:10:18: error: 'endl' was not declared in this scope
     cout<<"YES"<<endl;
                  ^~~~
/in/foo.cc:12:5: error: 'cout' was not declared in this scope
     cout<<"NO"<<endl;
     ^~~~
/in/foo.cc:12:17: error: 'endl' was not declared in this scope
     cout<<"NO"<<endl;
                 ^~~~