/in/foo.cc: In function 'void tarjan(int)':
/in/foo.cc:22:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<v[x].size();i++)
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'void hardlink()':
/in/foo.cc:55:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int x=0;x<v[i].size();x++)
               ~^~~~~~~~~~~~