#include<bits/stdc++.h>
using namespace std;
const int N = 100011;
int dp[N][2], pd[N][2];
#define pb push_back
int a[N];
const int inf = 1000000007;
vector<int> e[N];
void dfs(int v, int fa) {
	for(int d = 0; d < 2; d++) {
		dp[v][d] = 0;
	}
	int sons = e[v].size() - (fa != 0);
	if(sons) {
		dp[v][1] = -inf;
	}
	for(int y : e[v]) {
		if(y == fa) continue;
		dfs(y, v);
		
		for(int d = 0; d < 2; d++) {
			pd[v][d] = 0;
		}
		for(int d = 0; d < 2; d++) {
			for(int e = 0; e < 2; e++) {
				pd[v][d ^ e] = max(pd[v][d ^ e], dp[v][d] + dp[y][e]);
			}
		}
		for(int d = 0; d < 2; d++) {
			dp[v][d] = pd[v][d];
		}
	}
	
	dp[v][a[v] ^ 1]++;
}
int main() {
	int n;
	scanf("%d", &n);
	for(int i = 1; i <= n; i++) {
		scanf("%d", &a[i]);
	}
	for(int i = 1; i < n; i++) {
		int x, y;
		scanf("%d%d", &x, &y);

		e[x].pb(y);
		e[y].pb(x);
	}
	
	dfs(1,0);
	printf("%d\n", max(dp[1][0], dp[1][1]));
}