/in/foo.cc: In function 'void print_result(int)':
/in/foo.cc:7:26: error: 'pow' was not declared in this scope
  for (int i = 1; pow(2, i) <= num; i++)
                          ^
/in/foo.cc:10:14: error: 'pow' was not declared in this scope
  if (pow(2, k) == num) {
              ^