foo.cc: In function ‘int main()’:
foo.cc:22:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   22 |         for(int i=1;i<=s.size();i++){
      |                     ~^~~~~~~~~~