/in/foo.cc: In function 'int main()':
/in/foo.cc:6:8: error: 'cin' was not declared in this scope
  while(cin>>n){
        ^
/in/foo.cc:17:3: error: 'cout' was not declared in this scope
   cout<<fixed<<setprecision(2)<<t<<endl;
   ^
/in/foo.cc:17:36: error: 'endl' was not declared in this scope
   cout<<fixed<<setprecision(2)<<t<<endl;
                                    ^