#include<bits/stdc++.h>
using std::cin;
using std::cout;
const int N = 100005;
int n;
struct edge {
	int to, nxt;
} e[N << 1];
int h[N], num;
void link(int x, int y) {
	e[++num] = {y, h[x]}, h[x] = num;
	e[++num] = {x, h[y]}, h[y] = num;
}
int a[N];
int dp[N][2], deg[N];
void dfs0(int x, int fa = 0) {
	int leaf = 1;
	dp[x][1] = -1e9;
	for(int i = h[x];i;i = e[i].nxt) if(e[i].to != fa) {
		leaf = 0;
		dfs0(e[i].to, x);
		int w[2] = {-(int)1e9, -(int)1e9};
		int t = e[i].to;
		for(int a : {0, 1})
		for(int b : {0, 1})
			w[a ^ b] = std::max(w[a ^ b], dp[x][a] + dp[t][b]);
		dp[x][0] = w[0];
		dp[x][1] = w[1];
	}
	if(leaf) {
		dp[x][0] = dp[x][1] = 0;
	}
	dp[x][!a[x]] += 1;
}
int main() {
	std::ios::sync_with_stdio(false), cin.tie(0);
	cin >> n;
	for(int i = 1;i <= n;++i) cin >> a[i];
	for(int i = 1, x, y;i < n;++i) {
		cin >> x >> y;
		link(x, y);
	}
	dfs0(1);
	cout << std::max(dp[1][0], dp[1][1]) << '\n';
}