View Compilation Error

0_0_33218770_4919.cpp: In function 'int main()':
0_0_33218770_4919.cpp:23:9: error: 'cin' was not declared in this scope
  while (cin >> n && n != -1) {
         ^
0_0_33218770_4919.cpp:25:3: error: 'cout' was not declared in this scope
   cout << num1 << endl;
   ^
0_0_33218770_4919.cpp:25:19: error: 'endl' was not declared in this scope
   cout << num1 << endl;
                   ^