Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<map>

#include<cstring>

using namespace std;

int n,m;

#define MAXN 100010

int val[MAXN];

struct edge

{

    int to,nxt;

}e[MAXN << 1];

int edgenum = 0;

int lin[MAXN] = {0};

void add(int a,int b)

{

    ++edgenum;e[edgenum].to = b;e[edgenum].nxt = lin[a];lin[a] = edgenum;

    ++edgenum;e[edgenum].to = a;e[edgenum].nxt = lin[b];lin[b] = edgenum;

    return;

}

map<int,long long> s[MAXN];

int rt[MAXN];

long long dep[MAXN];

bool vis[MAXN];

void merge(int &rt,int &son)

{

    if(s[rt].size() < s[son].size())swap(rt,son);

    for(map<int,long long>::iterator i = s[son].begin();i != s[son].end();++i)

    {

        s[rt][i -> first] += i -> second;

    }

    return;

}

long long ans = 0;

void dfs(int k,int depth)

{

    vis[k] = true;dep[k] = depth;

    for(int i = lin[k];i != 0;i = e[i].nxt)

    {

        if(vis[e[i].to])continue;

        dfs(e[i].to,depth + val[e[i].to]);

        merge(rt[k],rt[e[i].to]);

    }

    ++s[rt[k]][dep[k]];

    map<int,long long>::iterator i = s[rt[k]].find(dep[k] + m);

    if(i != s[rt[k]].end())ans += i -> second;

    return;

}

int main()

{

    scanf("%d%d",&n,&m);

    for(int i = 1;i <= n;++i)scanf("%d",&val[i]);

    int a,b;

    for(int i = 1;i < n;++i)

    {

        scanf("%d%d",&a,&b);

        add(a,b);

    }

    for(int i = 1;i <= n;++i)rt[i] = i;

    dfs(1,val[1]);

    cout << ans + s[rt[1]][m] << endl;

    return 0;

}