// File catexercise.cpp created on 29.09.2025 at 14:27:20
#include <bits/stdc++.h>
using i64 = long long;
#ifdef DEBUG
#include "/home/ahmetalp/Desktop/Workplace/debug.h"
#else
#define debug(...) void(23)
#endif
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int N;
std::cin >> N;
std::vector<int> H(N);
for (int i = 0; i < N; ++i) {
std::cin >> H[i];
}
std::vector<std::vector<int>> adj(N);
for (int i = 1; i < N; ++i) {
int A, B;
std::cin >> A >> B;
--A, --B;
adj[A].emplace_back(B);
adj[B].emplace_back(A);
}
const int LG = std::__lg(N) + 1;
std::vector<int> dep(N);
std::vector<std::vector<int>> par(LG, std::vector<int>(N));
auto dfs = [&](auto&& self, int v) -> void {
for (auto u : adj[v]) {
if (u == par[0][v]) {
continue;
}
dep[u] = dep[v] + 1;
par[0][u] = v;
self(self, u);
}
};
dfs(dfs, 0);
for (int l = 1; l < LG; ++l) {
for (int i = 0; i < N; ++i) {
par[l][i] = par[l - 1][par[l - 1][i]];
}
}
auto lca = [&](int a, int b) -> int {
if (dep[a] > dep[b]) {
std::swap(a, b);
}
int dif = dep[b] - dep[a];
for (int l = 0; l < LG; ++l) {
if (dif >> l & 1) {
b = par[l][b];
}
}
if (a == b) {
return a;
}
for (int l = LG - 1; l >= 0; --l) {
if (par[l][a] != par[l][b]) {
a = par[l][a];
b = par[l][b];
}
}
return par[0][a];
};
auto dis = [&](int a, int b) -> int {
return dep[a] + dep[b] - 2 * dep[lca(a, b)];
};
std::vector<int> f(N);
std::iota(f.begin(), f.end(), 0);
auto get = [&](int x) -> int {
while (x != f[x]) {
x = f[x] = f[f[x]];
}
return x;
};
auto unite = [&](int a, int b) -> bool {
a = get(a), b = get(b);
if (a == b) {
return false;
}
f[a] = b;
return true;
};
std::vector<i64> ans(N);
std::vector<int> act(N), ord(N);
std::iota(ord.begin(), ord.end(), 0);
std::sort(ord.begin(), ord.end(), [&](auto lhs, auto rhs) {
return H[lhs] < H[rhs];
});
for (auto i : ord) {
act[i] = true;
for (auto j : adj[i]) {
if (!act[j]) {
continue;
}
j = get(j);
ans[i] = std::max(ans[i], ans[j] + dis(i, j));
unite(j, i);
}
}
std::cout << ans[ord[N - 1]] << '\n';
return 0;
}
