/in/foo.cc: In function 'int main()':
/in/foo.cc:42:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i = 0; i < end.size(); i++){
                    ~~^~~~~~~~~~~~
/in/foo.cc:52:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < end.size(); i++){
                   ~~^~~~~~~~~~~~
/in/foo.cc:64:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < end.size(); i++){
                   ~~^~~~~~~~~~~~