foo.cc: In function 'int main()':
foo.cc:15:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   15 |  while (temp >= b.length())
      |         ~~~~~^~~~~~~~~~~~~
foo.cc:27:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |  for (int i = 0; i < a.length(); i++)
      |                  ~~^~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务