https://www.acwing.com/problem/content/4949/

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 100010, M = 2 * N;
int e[M], ne[M], c[N], h[N], idx;
int n, m;
int s;

void add(int a, int b){
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++;
}

int dfs(int u, int fa, bool ok, int cnt){
    if(c[u] == 1) cnt ++;
    else cnt = 0;
    if(cnt > m) ok = true;

    int res = 0, sons = 0;
    for(int i = h[u]; i != -1; i = ne[i]){
        int j = e[i];
        if(j == fa) continue;
        sons ++;
        res += dfs(j, u, ok, cnt);
    }  

    if(!sons){
        s ++;
    }

    if(!sons && ok) {
        res ++;
    }
    return res;
}
int main ()
{
    cin >> n >> m;
    memset(h, -1, sizeof h);

    for(int i = 1; i <= n; i ++) cin >> c[i];
    for(int i = 0; i < n - 1; i ++){
        int a, b;
        cin >> a >> b;
        add(a, b), add(b, a);
    }
    int d = dfs(1, -1, false, 0);
    cout << s - d << endl;
    return 0;
}