foo.cc: In function ‘int countTotalCircles(std::string)’:
foo.cc:44:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   44 |         for(int i=0;i<num.length();i++) cnt += countCircles(num[i]);
      |                     ~^~~~~~~~~~~~~