#pragma GCC optimize("O2")
#include <algorithm>
#include <array>
#include <bit>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfenv>
#include <cfloat>
#include <chrono>
#include <cinttypes>
#include <climits>
#include <cmath>
#include <compare>
#include <complex>
#include <concepts>
#include <cstdarg>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <new>
#include <numbers>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <ranges>
#include <set>
#include <span>
#include <sstream>
#include <stack>
#include <streambuf>
#include <string>
#include <tuple>
#include <type_traits>
#include <variant>

#define int ll
#define INT128_MAX (__int128)(((unsigned __int128) 1 << ((sizeof(__int128) * __CHAR_BIT__) - 1)) - 1)
#define INT128_MIN (-INT128_MAX - 1)

namespace R = std::ranges;
namespace V = std::views;

using namespace std;

using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<long long, long long>;
using tiii = tuple<int, int, int>;
using ldb = long double;
//#define double ldb

template<class T>
ostream& operator<<(ostream& os, const pair<T, T> pr) {
  return os << pr.first << ' ' << pr.second;
}
template<class T, size_t N>
ostream& operator<<(ostream& os, const array<T, N> &arr) {
  for(const T &X : arr)
    os << X << ' ';
  return os;
}
template<class T>
ostream& operator<<(ostream& os, const vector<T> &vec) {
  for(const T &X : vec)
    os << X << ' ';
  return os;
}


signed main() {
  ios::sync_with_stdio(false), cin.tie(NULL);

  int n; cin >> n;
  vector<int> a(n);
  for(int &x : a)
    cin >> x;
  vector<vector<int>> g(n);
  for(int i = 1; i < n; i++) {
    int u, v; cin >> u >> v;
    u--, v--;
    g[u].emplace_back(v);
    g[v].emplace_back(u);
  }

  auto merge = [](array<int, 2> l, array<int, 2> r) {
    array<int, 2> res = {};
    for(int i : {0, 1})
      for(int j : {0, 1})
        res[i ^ j] = max(res[i ^ j], l[i] + r[j]);
    return res;
  };

  vector<array<int, 2>> dp(n, {-1, -1});
  auto dfs = [&](int v, int p, auto self) -> void {
    for(int x : g[v]) {
      if (x == p) continue;
      self(x, v, self);
      if (dp[v][0] == -1)
        dp[v] = dp[x];
      else
        dp[v] = merge(dp[v], dp[x]);
    }
    if (dp[v][0] == -1)
      dp[v] = {0, 0};
    dp[v][a[v] ^ 1]++;
  };

  dfs(0, -1, dfs);

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

  return 0;
}