#include <algorithm>
#include <iostream>
#include <set>
#include <vector>

using namespace std;
using ll = long long;

#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define all(v) begin(v), end(v)

template <class T> bool chmin(T &dst, T src) {
  if (dst > src) {
    dst = src;
    return true;
  }
  return false;
}

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);

  int n;
  cin >> n;
  vector<int> w(n);
  rep(i, n) cin >> w[i];
  vector<vector<int>> graph(n);
  rep(i, n - 1) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    graph[a].emplace_back(b);
    graph[b].emplace_back(a);
  }

  vector<ll> sum(all(w));
  auto dfs1 = [&](auto &&f, int i, int p) -> ll {
    for (auto &c : graph[i]) {
      if (c == p) continue;
      sum[i] += f(f, c, i);
    }
    return sum[i];
  };
  dfs1(dfs1, 0, -1);

  ll total = sum[0];

  ll ans = 1LL << 60;
  auto update = [&](ll s1, ll s2) {
    auto [mn, mx] = minmax({s1, s2, total - s1 - s2});
    chmin(ans, mx - mn);
  };

  auto dfs2 = [&](auto &&f, int i, int p) -> set<ll> {
    set<ll> sums;
    ll current = sum[i];
    ll remain = total - current;
    for (auto &c : graph[i]) {
      if (c == p) continue;
      set<ll> res = f(f, c, i);

      {
        auto itr = res.lower_bound(current / 2);
        if (itr != res.begin()) update(remain, *--itr);
      }

      if (sums.size() < res.size()) swap(sums, res);

      for (auto e : res) {
        auto itr = sums.lower_bound((total - e) / 2);
        if (itr != res.end()) update(e, *itr);
        if (itr != res.begin()) update(e, *--itr);
      }

      sums.insert(all(res));
    }
    sums.insert(current);
    return sums;
  };

  dfs2(dfs2, 0, -1);

  cout << ans << endl;
}