dfs.cpp

LL dfs(int v, int p, int k) {
  int rem = k - 2*(sz[v]-mx[v]);
  if (rem <= 0) return 0;
  
  LL ret = INF;
  int u;
  LL l;
  for (auto &e : es[v]) {
    u = e.to;
    if (u == p) continue;
    if (sz[u] != mx[v]) continue;
    l = e.len;
    break;
  }
  return dfs(u, v, rem) + l * rem;
}