/in/foo.cc: In function 'void match(std::__cxx11::string&, int)':
/in/foo.cc:6:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     while(k < s.length()){
           ~~^~~~~~~~~~~~
/in/foo.cc:11:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while(k < s.length() && w < limit && l < limit){
               ~~^~~~~~~~~~~~
/in/foo.cc:16:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while(k < s.length() && f(w - l) == 1){
               ~~^~~~~~~~~~~~
/in/foo.cc:24:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(k == 0 || (k == s.length() && w == 0 && l == 0))
                   ~~^~~~~~~~~~~~~