/in/foo.cc: In function 'bool SPFA(int, int)':
/in/foo.cc:97:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int z = 0; z < edge[x].size(); z++)
                         ~~^~~~~~~~~~~~~~~~
/in/foo.cc: In function 'newpair ZKW_DFS(int, int, int)':
/in/foo.cc:158:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int& z = head[x]; z < edge[x].size(); z++)
                            ~~^~~~~~~~~~~~~~~~
/in/foo.cc: In function 'void costflow()':
/in/foo.cc:187:40: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
         while (ans = ZKW_DFS(0, st, inf))
                                        ^