#include <bits/stdc++.h>
using namespace std;
#define all(v) v.begin(), v.end()
typedef long long ll;
const int NMAX = 2e5 + 5;
ll n, h[NMAX], a, b, lv[NMAX], p[NMAX][18], par[NMAX], dp[NMAX];
vector<int> adj[NMAX];
int find(int x){return par[x] == -1 ? x : par[x] = find(par[x]);}
void dfs(int x, int par){
for(int& nx : adj[x]){
if(nx == par) continue;
p[nx][0] = x;
lv[nx] = lv[x] + 1;
dfs(nx, x);
}
return;
}
int dist(int a, int b){
int ret = 0;
if(lv[a] < lv[b]) swap(a, b);
for(int i = 17; i >= 0; i--)
if(lv[a] - lv[b] >= 1 << i){
a = p[a][i];
ret += 1 << i;
}
if(a == b) return ret;
for(int i = 17; i >= 0; i--)
if(p[a][i] != p[b][i]){
a = p[a][i];
b = p[b][i];
ret += 1 << (i + 1);
}
return ret + 2;
}
int main(void){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n;
for(int i = 1; i <= n; i++) cin >> h[i];
for(int i = 1; i < n; i++){
cin >> a >> b;
adj[h[a]].emplace_back(h[b]);
adj[h[b]].emplace_back(h[a]);
}
dfs(1, -1);
for(int j = 1; j < 18; j++)
for(int i = 1; i <= n; i++)
p[i][j] = p[p[i][j - 1]][j - 1];
memset(par, -1, sizeof(par));
for(int i = 1; i <= n; i++){
for(int j : adj[i]){
j = find(j);
if(j > i) continue;
dp[i] = max(dp[i], dp[j] + dist(i, j));
par[j] = i;
}
}
cout << dp[n];
return 0;
}
