/in/foo.cc: In function 'int main()':
/in/foo.cc:23:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<road.length();i++){
              ~^~~~~~~~~~~~~~
/in/foo.cc:31:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<pos1.size();i++){
              ~^~~~~~~~~~~~