#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 2e5, KMAX = 20;
int n, h[N + 5], euler[2*N + 5], lg[2*N + 5], tin[N + 5], tout[N + 5], timer = 1, d[N + 5], table[2*N + 5][KMAX + 5];
vector<int> adj[N + 5];
void dfs1(int u, int e) {
tin[u] = ++timer;
euler[timer] = u;
for (auto&v : adj[u]) {
if (v == e) continue;
d[v] = d[u] + 1;
dfs1(v, u);
euler[++timer] = u;
}
tout[u] = timer;
}
int combine(int x, int y) { return d[x] < d[y] ? x : y; }
void build(int n) {
lg[1] = 0;
for (int i = 2; i <= n; i++) lg[i] = lg[i/2] + 1;
for (int i = 1; i <= n; i++) table[i][0] = euler[i];
for (int j = 1; j <= KMAX; j++) {
for (int i = 1; i + (1ll << j) - 1 <= n; i++) {
table[i][j] = combine(table[i][j - 1], table[i + (1ll << (j - 1))][j - 1]);
}
}
}
int lca(int x, int y) {
if (tin[x] > tin[y]) swap(x, y);
int k = lg[tin[y] - tin[x] + 1], w = combine(table[tin[x]][k], table[tin[y] - (1ll << k) + 1][k]);
return d[x] + d[y] - 2*d[w];
}
int par[N + 5], sz[N + 5], mx[N + 5], highest[N + 5], indx[N + 5];
int find(int x) { return x == par[x] ? x : find(par[x]); }
bool same(int x, int y) { return find(x) == find(y); }
int combine2(int x, int y) {
if (!x) return y;
else if (!y) return x;
else return h[x] > h[y] ? x : y;
}
void unite(int x, int y) {
x = find(x), y = find(y);
if (sz[x] < sz[y]) swap(x, y);
sz[x] += sz[y], par[y] = x;
mx[x] = max(mx[x], mx[y]), highest[x] = combine2(highest[x], highest[y]);
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
for (int i = 1; i <= n; i++) cin >> h[i];
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
dfs1(1, 0);
build(2*n);
fill(sz + 1, sz + n + 1, 1ll);
iota(par + 1, par + n + 1, 1ll);
iota(highest + 1, highest + n + 1, 1ll);
iota(indx + 1, indx + n + 1, 1ll);
sort(indx + 1, indx + n + 1, [&](int a, int b) { return h[a] < h[b]; });
for (int i = 1;i <= n; i++) {
int index = indx[i];
for (auto&v : adj[index]) {
int root = find(v);
if (h[highest[root]] > h[index]) continue;
mx[index] = max(mx[index], mx[root] + lca(index, highest[root]));
}
for (auto&v : adj[index]) {
int root = find(v);
if (h[highest[root]] > h[index]) continue;
if (!same(index, v)) unite(index, v);
}
}
cout << *max_element(mx + 1, mx + n + 1) << '\n';
return 0;
}
