/in/foo.cc: In function 'int main()':
/in/foo.cc:9:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    9 |         while(isdigit(s[i])&&i<s.size())//算第一个数
      |                              ~^~~~~~~~~
/in/foo.cc:15:15: 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(;i<s.size();)
      |              ~^~~~~~~~~
/in/foo.cc:18:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   18 |                 while(isdigit(s[i])&&i<s.size())
      |                                      ~^~~~~~~~~