/in/foo.cc: In function 'int main()':
/in/foo.cc:26:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int x=0; x<v[i].size(); x++)
                ~^~~~~~~~~~~~
/in/foo.cc:28:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int z=x+1; z<v[i].size(); z++)
                   ~^~~~~~~~~~~~