foo.cc: In function ‘int Countxiaoxie(std::string&)’:
foo.cc:7:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    7 |         for(int i=0; i<s.length(); i++)
      |                      ~^~~~~~~~~~~
foo.cc: In function ‘int Countdaxie(std::string&)’:
foo.cc:15:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   15 |         for(int i=0; i<s.length(); i++)
      |                      ~^~~~~~~~~~~