#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;
using ll = long long;
#define rep(i, s, t) for (ll i = s; i < (ll)(t); i++)
#define all(x) begin(x), end(x)
template <class T> bool chmin(T& x, T y) {
	return x > y ? (x = y, true) : false;
}
template <class T> bool chmax(T& x, T y) {
	return x < y ? (x = y, true) : false;
}

void solve() {
	int n;
	cin >> n;
	vector<int> s(n);
	rep(i, 0, n) cin >> s[i];
	vector<vector<int>> g(n);
	rep(i, 0, n - 1) {
		int a, b;
		cin >> a >> b;
		a--, b--;
		g[a].push_back(b);
		g[b].push_back(a);
	}
	ll ans = 0;
	auto dfs = [&](auto self, int nw, int pr) -> pair<ll, ll> {
		ll mx = 0, mn = 0;
		for (int nx : g[nw]) {
			if (nx == pr) continue;
			auto [x, y] = self(self, nx, nw);
			if (s[nw] < s[nx]) chmax(mx, x);
			if (s[nw] > s[nx]) chmax(mn, y);
		}
		mx += s[nw], mn += s[nw];
		chmax(ans, max(mx, mn));
		return {mx, mn};
	};
	dfs(dfs, 0, -1);
	cout << ans << '\n';
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout << fixed << setprecision(15);
	int t = 1;
	// cin >> t;
	while (t--) solve();
}