//#pragma GCC optimize("Ofast", "unroll-loops")
//#pragma GCC target("sse", "sse2", "sse3", "ssse3", "sse4")

#ifdef __APPLE__
#include <iostream>
#include <cmath>
#include <algorithm>
#include <stdio.h>
#include <cstdint>
#include <cstring>
#include <string>
#include <cstdlib>
#include <vector>
#include <bitset>
#include <map>
#include <queue>
#include <ctime>
#include <stack>
#include <set>
#include <list>
#include <random>
#include <deque>
#include <functional>
#include <iomanip>
#include <sstream>
#include <fstream>
#include <complex>
#include <numeric>
#include <cassert>
#include <array>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <thread>
#else
#include <bits/stdc++.h>
#endif

#define all(a) a.begin(),a.end()
#define len(a) (int)(a.size())
#define mp make_pair
#define pb push_back
#define fir first
#define sec second
#define fi first
#define se second

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
typedef long double ld;

template<typename T>
bool umin(T &a, T b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}
template<typename T>
bool umax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

#if __APPLE__
#define D for (bool _FLAG = true; _FLAG; _FLAG = false)
#define LOG(...) print(#__VA_ARGS__" ::", __VA_ARGS__) << endl
template <class ...Ts> auto &print(Ts ...ts) { return ((cerr << ts << " "), ...); }
#else
#define D while (false)
#define LOG(...)
#endif

const int max_n = 100111, inf = 1000111222;

int n, a[max_n], dp[max_n][2];
vector<int> g[max_n];

void dfs(int v, int p) {
    bool is_leaf = true;
    for (int to : g[v]) {
        if (to == p) {
            continue;
        }
        is_leaf = false;
        dfs(to, v);
    }
    vector<int> cur_dp(2);
    if (!is_leaf) {
        cur_dp[1] = -inf;
    }
    for (int to : g[v]) {
        if (to == p) {
            continue;
        }
        vector<int> ndp(2);
        for (int i = 0; i < 2; ++i) {
            for (int j = 0; j < 2; ++j) {
                ndp[i ^ j] = max(ndp[i ^ j], cur_dp[i] + dp[to][j]);
            }
        }
        cur_dp = ndp;
    }
    dp[v][0] = cur_dp[0];
    dp[v][1] = cur_dp[1];
    ++dp[v][a[v] ^ 1];
}

int main() {
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);

    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> n;
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }
    for (int i = 1; i < n; ++i) {
        int u, v;
        cin >> u >> v;
        --u;
        --v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    dfs(0, -1);
    cout << max(dp[0][0], dp[0][1]) << "\n";
}