/in/foo.cc: In function 'void tarjan(int)':
/in/foo.cc:19:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<g[u].size();i++){
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:63:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<g[i].size();j++){
               ~^~~~~~~~~~~~