/in/foo.cc: In function 'void bfs(int)':
/in/foo.cc:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<anti_cn[now].size();++i)
                     ~^~~~~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:44:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int j=0;j<cn[i].size();++j)
                     ~^~~~~~~~~~~~~