/in/foo.cc: In function 'bool bfs(int)':
/in/foo.cc:66:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<g[ bg ].size();i++)
               ~^~~~~~~~~~~~~~~
/in/foo.cc: In function 'int spfa(int)':
/in/foo.cc:104:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<g[ bg ].size();i++)
               ~^~~~~~~~~~~~~~~