思路：

AC代码：

#include "iostream"#include "string.h"#include "stack"#include "queue"#include "string"#include "vector"#include "set"#include "map"#include "algorithm"#include "stdio.h"#include "math.h"#pragma comment(linker, "/STACK:102400000,102400000")#define ll long long#define endl ("\n")#define bug(x) cout<
     
      <<" "<<"UUUUU"<
      
       =k) ans+=w*k;    else ans+=w*siz[u];}void add(int u, int v, int w){    to[tot]=v;    nex[tot]=head[u];    wi[tot]=w;    head[u]=tot++;}int main(){    while(scanf("%d %d",&n, &k)!=EOF){        mem(head,-1),tot=0;        int u,v;        ll w;        for(int i=1; i