/in/foo.cc: In function 'int main()':
/in/foo.cc:55:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |     for (i = 0; i < s.size(); i++) mid.push_back(s[i]);
      |                 ~~^~~~~~~~~~
/in/foo.cc:57:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   57 |     for (i = 0; i < s.size(); i++) suc.push_back(s[i]);
      |                 ~~^~~~~~~~~~