#include <bits/stdc++.h>

using namespace std;
using lint = int64_t;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int N; cin >> N;

    vector<int> A(N); for (int& a : A) cin >> a;

    vector<vector<int>> adj(N);
    for (int i = 0; i+1 < N; ++i) {
        int a, b; cin >> a >> b;
        --a, --b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }

    vector<vector<int>> dp(N, vector<int>(2));
    const int INF = INT_MAX/2;
    auto dfs = [&](auto&& self, int cur, int prv) -> void {
        dp[cur] = {0, -INF};
        bool is_leaf = true;
        for (int nxt : adj[cur]) {
            if (nxt == prv) continue;
            self(self, nxt, cur);
            is_leaf = false;
            vector<int> ndp(2, -INF);
            for (int a = 0; a < 2; ++a) {
                for (int b = 0; b < 2; ++b) {
                    ndp[a^b] = max(ndp[a^b], dp[cur][a] + dp[nxt][b]);
                }
            }
            dp[cur].swap(ndp);
        }
        if (is_leaf) {
            dp[cur] = {0, 1};
        } else {
            dp[cur][A[prv]^1] += 1;
        }
    };


    dfs(dfs, 0, -1);
    cout << max(dp[0][0], dp[0][1]) << '\n';
}