/in/foo.cc: In function 'int main()':
/in/foo.cc:5:2: error: 'cin' was not declared in this scope
  cin>>n;
  ^~~
/in/foo.cc:12:4: error: 'cout' was not declared in this scope
    cout<<" ";
    ^~~~
/in/foo.cc:17:4: error: 'cout' was not declared in this scope
    cout<<"#";
    ^~~~
/in/foo.cc:21:3: error: 'cout' was not declared in this scope
   cout<<endl;
   ^~~~
/in/foo.cc:21:9: error: 'endl' was not declared in this scope
   cout<<endl;
         ^~~~
/in/foo.cc:4:7: warning: unused variable 'a' [-Wunused-variable]
  char a='a';
       ^