/in/foo.cc: In function 'std::__cxx11::string change(std::__cxx11::string)':
/in/foo.cc:9:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.length();i++){
              ~^~~~~~~~~~~
/in/foo.cc:10:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(s[i+1]==' '||i==s.length()-1){
                   ~^~~~~~~~~~~~~~
/in/foo.cc:14:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if(i==s.length()-1)continue;
       ~^~~~~~~~~~~~~~