/in/foo.cc:10:11: error: '::main' must return 'int'
 void main()
           ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:15:35: error: 'scanf_s' was not declared in this scope
  while (scanf_s("%s", arr, 1000001))
                                   ^
/in/foo.cc:17:23: error: 'strlen' was not declared in this scope
   int len = strlen(arr);
                       ^