/in/foo.cc: In function 'std::string Plus(std::string, std::string)':
/in/foo.cc:26:11: warning: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
   26 |  while (i < x)
      |         ~~^~~
/in/foo.cc:49:12: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   49 |   while (i < a.size())
      |          ~~^~~~~~~~~~
/in/foo.cc:67:12: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   67 |   while (i < b.size())
      |          ~~^~~~~~~~~~