#include <bits/stdc++.h>
#define pw2(i) (1LL << (i))
#define all(v) (v).begin(), (v).end()
using namespace std;
using ll = long long;
/*------------- I alone decide my fate ! -------------*/
int N, p[200009], id[200009];
vector <int> adj[200009];
ll dp[200009];
int parent[200009], sz[200009], ma[200009];
void make_set(int v) {
sz[v] = 1;
parent[v] = v;
ma[v] = v;
}
int find(int v) {
if (v == parent[v]) return v;
return parent[v] = find(parent[v]);
}
void onion(int a, int b) {
a = find(a);
b = find(b);
if (a != b) {
if (sz[a] < sz[b]) swap(a, b);
sz[a] += sz[b];
parent[b] = a;
ma[a] = (p[ma[a]] > p[ma[b]] ? ma[a] : ma[b]);
}
}
const int MAXN = 200009;
const int LOG = 20;
int up[MAXN][LOG];
int depth_arr[MAXN];
void dfs_lca(int u, int parent_node) {
up[u][0] = parent_node;
for (int j = 1; j < LOG; ++j) up[u][j] = up[ up[u][j-1] ][j-1];
for (int v : adj[u]) {
if (v == parent_node) continue;
depth_arr[v] = depth_arr[u] + 1;
dfs_lca(v, u);
}
}
int lca(int a, int b) {
if (depth_arr[a] < depth_arr[b]) swap(a, b);
int k = depth_arr[a] - depth_arr[b];
for (int j = 0; j < LOG; ++j) if (k & (1<<j)) a = up[a][j];
if (a == b) return a;
for (int j = LOG-1; j >= 0; --j) {
if (up[a][j] != up[b][j]) {
a = up[a][j];
b = up[b][j];
}
}
return up[a][0];
}
int dist(int a, int b) {
int c = lca(a, b);
return depth_arr[a] + depth_arr[b] - 2 * depth_arr[c];
}
void solve() {
cin >> N;
for (int i = 1; i <= N; i ++) {
id[i] = i;
cin >> p[i];
}
for (int i = 1; i < N; i ++) {
int u, v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
depth_arr[1] = 0;
dfs_lca(1, 1);
sort(id + 1, id + N + 1, [] (int x, int y) {
return p[x] < p[y];
});
for (int i = 1; i <= N; i ++) {
make_set(i);
}
for (int i = 1; i <= N; i ++) {
int u = id[i];
for (auto v : adj[u]) {
if (p[v] < p[u]) {
dp[u] = max(dp[u], dp[ma[find(v)]] + dist(u, ma[find(v)]) );
onion(u, v);
}
}
}
cout << dp[id[N]];
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
solve();
return 0;
}
/*
How can you see into my eyes, like open doors?
Leading you down into my core, where I've become so numb
Without a soul, my spirit's sleeping somewhere cold
Until you find it here and bring it back home!
Wake me up! Wake me up inside
Can't wake up? Wake me up inside
*/
