/in/foo.cc: In function 'int main()':
/in/foo.cc:14:2: error: 'cin' was not declared in this scope
  cin>>n;
  ^~~
/in/foo.cc:27:4: error: 'cout' was not declared in this scope
    cout<<"YES"<<endl;
    ^~~~
/in/foo.cc:27:17: error: 'endl' was not declared in this scope
    cout<<"YES"<<endl;
                 ^~~~
/in/foo.cc:29:4: error: 'cout' was not declared in this scope
    cout<<"NO"<<endl;
    ^~~~
/in/foo.cc:29:16: error: 'endl' was not declared in this scope
    cout<<"NO"<<endl;
                ^~~~