/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:20:36: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
     for (int i = h[u], v; v = tto[i]; i = nxt[i]) {
                                    ^
/in/foo.cc: In function 'int bfs()':
/in/foo.cc:59:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < vec.size(); i++) {
                         ~~^~~~~~~~~~~~
/in/foo.cc:61:44: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
             for (int j = h[u], v; v = tto[j]; j = nxt[j]) {
                                            ^