#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  } 
  vector<vector<int>> g(n);
  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);
  }
  vector<vector<int>> dp(n, vector<int>(2));
  function<void(int, int)> Dfs = [&](int v, int pv) {
    bool leaf = true;
    dp[v][1] = int(-1e9);
    for (int u : g[v]) {
      if (u == pv) {
        continue;
      }
      Dfs(u, v);
      leaf = false;
      vector<int> new_dp(2);
      for (int x = 0; x < 2; x++) {
        for (int y = 0; y < 2; y++) {
          new_dp[x ^ y] = max(new_dp[x ^ y], dp[v][x] + dp[u][y]);
        }
      }
      swap(dp[v], new_dp);
    }
    if (leaf) {
      dp[v][a[v] ^ 1] = 1;
      dp[v][a[v]] = 0;
    } else {
      dp[v][a[v] ^ 1] += 1;
    }
  };
  Dfs(0, 0);
  cout << max(dp[0][0], dp[0][1]) << '\n';
  return 0;
}