/in/foo.cc: In function 'std::string addOne(std::string)':
/in/foo.cc:11:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   11 |     for (int i = 0; i < s.size() && carry; i++) {
      |                     ~~^~~~~~~~~~
/in/foo.cc: In function 'std::string mul(std::string, std::string)':
/in/foo.cc:27:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |     for (int i = 0; i < a.size(); i++) {
      |                     ~~^~~~~~~~~~
/in/foo.cc:29:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |         for (int j = 0; j < b.size(); j++) {
      |                         ~~^~~~~~~~~~
/in/foo.cc: In function 'std::string subOne(std::string)':
/in/foo.cc:51:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   51 |     for (int i = 0; i < s.size() && borrow; i++) {
      |                     ~~^~~~~~~~~~