//
// Created by adavy on 5/11/2025.
//
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
vector<vector<int>> adj;
// to calculate distances
vector<vector<int>> par; vector<int> dep;
void dfs(int u, int p){
par[u][0] = p;
for(auto&v:adj[u]) if (v != p){
dep[v] = dep[u] + 1;
dfs(v,u);
}
}
int lca(int a, int b){
if (dep[a] < dep[b]) swap(a,b);
// dep[a] >= dep[b]
for(int j=0;j<20;++j) if ((1<<j)&(dep[a]-dep[b])) a = par[a][j];
if (a == b) return a;
for(int j=19;j>=0;--j) if (par[a][j] != par[b][j]){
a = par[a][j];
b = par[b][j];
}
return par[a][0];
}
int dist(int a, int b){
return dep[a] + dep[b] - 2*dep[lca(a,b)];
}
struct dsu{
vector<int> rep;
vector<int> key;
dsu(int n){
rep.resize(n);
key.resize(n);
for(int i=0;i<n;++i){
rep[i] = i;
key[i] = i;
}
}
int find(int u){
if (rep[u] == u) return u;
return rep[u] = find(rep[u]);
}
void unite(int a, int b){
// a is the new key
if (find(a) == find(b)) return;
int fa = find(a);
int fb = find(b);
rep[fb] = fa;
key[fa] = a;
}
int get_key(int u){
return key[find(u)];
}
};
int main(){
int N; cin >> N;
adj.resize(N);
vector<int> height(N);
par.resize(N, vector<int>(20, -1));
dep.resize(N, 0);
for(int i=0;i<N;++i){
cin >> height[i];
}
for(int i=0;i<(N-1);++i){
int a, b; cin >> a >> b; a--; b--;
adj[a].push_back(b);
adj[b].push_back(a);
}
// calculate distances
dfs(0, -1);
for(int j=1;j<20;++j){
for(int i=0;i<N;++i){
if (par[i][j-1] != -1){
par[i][j] = par[par[i][j-1]][j-1];
}
}
}
vector<int> order;
for(int i=0;i<N;++i){
order.push_back(i);
}
sort(order.begin(), order.end(), [&](int a, int b){
return height[a] < height[b];
});
vector<ll> dp(N, 0);
dsu d(N);
for(auto&u:order){
for(auto&v:adj[u]){
if (height[v] > height[u]) continue;
int keyv = d.get_key(v);
dp[u] = max(dp[u], dist(u, keyv) + dp[keyv]);
d.unite(u, v);
}
}
cout << dp[order[N-1]] << endl;
}
