/in/foo.cc: In function 'newpair ZKW_DFS(int, int, int)':
/in/foo.cc:128:34: error: cannot bind non-const lvalue reference of type 'unsigned int&' to a value of type 'int'
  128 |     for (unsigned int& z = head[x]; z < edge[x].size(); z++) {
      |                            ~~~~~~^
/in/foo.cc: In function 'void costflow()':
/in/foo.cc:154:20: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  154 |         while (ans = ZKW_DFS(0, st, inf)) {
      |                ~~~~^~~~~~~~~~~~~~~~~~~~~