/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:5:9: error: 'n' was not declared in this scope
  cin >> n;
         ^
/in/foo.cc:7:2: error: 'arr' was not declared in this scope
  arr[0] = 1;
  ^~~
/in/foo.cc:15:3: error: 'cout' was not declared in this scope
   cout <<arr[i]<<" ";
   ^~~~