View Compilation Error

0_0_37599141_4299.cpp: In function 'int main()':
0_0_37599141_4299.cpp:6:2: error: 'cin' was not declared in this scope
  cin >> s;
  ^
0_0_37599141_4299.cpp:12:3: error: 'cout' was not declared in this scope
   cout << k + n << endl;
   ^
0_0_37599141_4299.cpp:12:20: error: 'endl' was not declared in this scope
   cout << k + n << endl;
                    ^