foo.cc: In function ‘int main()’:
foo.cc:14:30: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   14 |                 for(int i=1;i<=e.size();i++){
      |                             ~^~~~~~~~~~