/in/foo.cc: In function 'void get_next(std::__cxx11::string)':
/in/foo.cc:11:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     while (r <= s.length()) {
            ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'll solve(std::__cxx11::string)':
/in/foo.cc:24:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     while (r < s.length()) {
            ~~^~~~~~~~~~~~