View Compilation Error

0_0_31727907_14955.cpp: In function 'int main()':
0_0_31727907_14955.cpp:12:8: error: 'cin' was not declared in this scope
  while(cin >> n&&n!=EOF)
        ^
0_0_31727907_14955.cpp:13:2: error: 'cout' was not declared in this scope
  cout << op(n) << endl;
  ^
0_0_31727907_14955.cpp:13:19: error: 'endl' was not declared in this scope
  cout << op(n) << endl;
                   ^