/in/foo.cc: In function 'bool duic(std::__cxx11::string)':
/in/foo.cc:6:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.length();i++){
               ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:27:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<str.size();i++){
               ^