/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:13:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0;i < G2[u].size();i++)
                   ~~^~~~~~~~~~~~~~
/in/foo.cc: In function 'int dfs2(int)':
/in/foo.cc:24:21: 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 bfs(int)':
/in/foo.cc:42:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for(int j = 0;j < G[Q[i]].size();j++)
                           ~~^~~~~~~~~~~~~~~~