#include<iostream>

#include<cstring>

#include<cstdio>

#include<algorithm>

#include<vector>

#define maxn 10100

using namespace std;

const int INF = 0x3f3f3f3f;

vector<int>G[maxn];

void insert(int be, int en) {

	G[be].push_back(en);

}

int n, m;

int h[maxn];

int b[maxn];

int vis[maxn];

int dfs(int x, int fa) {

	h[x] = 1;

	b[x] = 1;

	if (vis[x] == 0) {

		b[x] = INF;

	}

	if (vis[x] == 1) {

		h[x] = INF;

	}

	for (int i = 0; i < G[x].size(); i++) {

		int p = G[x][i];

		if (p == fa) continue;

		dfs(p, x);

		h[x] += min(b[p], h[p] - 1);

		b[x] += min(h[p], b[p] - 1);

	}

	return 0;

}

int main() {

	memset(vis, -1, sizeof(vis));

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

	int op;

	for (int i = 1; i <= m; i++) {

		scanf("%d", &op);

		vis[i] = op;

	}

	int be, en;

	int root = n;

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

		scanf("%d %d", &be, &en);

		insert(be, en);

		insert(en, be);

	}

	dfs(n, -1);

	printf("%d\n", min(h[n], b[n]));

	return 0;

}