/in/foo.cc: In function 'void spfa(int)':
/in/foo.cc:38:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0;i < G[pos].size();i ++){
                  ~~^~~~~~~~~~~~~~~
/in/foo.cc:56:25: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long long int' [-Wformat=]
     printf("%d\n",dis[i]);
                         ^