#include <bits/stdc++.h>
using namespace std;
#define int long long
int n;
vector<int> parent;
vector<bool> already;
vector<vector<int>> adj;
vector<int> vaut;
vector<vector<int>> adjbase;
vector<int> depth;
vector<vector<int>> up;
//LCA
int get_lca(int a, int b) {
if (depth[a] < depth[b]) swap(a, b);
int k=depth[a]-depth[b];
for (int j=19; j>=0; j--) {
if (k & (1<<j)) {
a=up[a][j];
}
}
if (a==b) return a;
for (int j=19; j>=0; j--) {
if (up[a][j]!=up[b][j]) {
a=up[a][j];
b=up[b][j];
}
}
return up[a][0];
}
//UNION FIND
int getparent(int x) {
if (x==parent[x]) return x;
return parent[x]=getparent(parent[x]);
}
bool same(int a, int b) {
return (getparent(a)==getparent(b));
}
void unite(int a, int b) {
if (!already[a]) return;
a=getparent(a);
b=getparent(b);
parent[a]=b;
adj[b].push_back(a);
}
//INIT
void initdfs(int s, int last=-1) {
for (auto u: adjbase[s]) {
if (u==last) continue;
depth[u] = depth[s]+1;
up[u][0]=s;
for (int i=1; i<20; i++) {
up[u][i]=up[ up[u][i-1] ][i-1];
}
initdfs(u, s);
}
}
//ANS CALCULATION
int calcans(int s) {
int ans=0;
for (auto u: adj[s]) {
int add=depth[u]+depth[s]-2LL*depth[get_lca(u, s)];
ans=max(ans, calcans(u)+add);
}
return ans;
}
void solve() {
cin >> n;
adj.resize(n+1);
already.resize(n+1, false);
adjbase.resize(n+1);
vaut.resize(n+1);
parent.resize(n+1);
depth.resize(n+1);
up.resize(n+1, vector<int>(20));
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
for (int i=0; i<n; i++) {
parent[i]=i;
}
for (int i=0; i<n; i++) {
int u; cin >> u;
pq.push({u, i});
}
for (int i=0; i<n-1; i++) {
int u, v; cin >> u >> v;
u--, v--;
adjbase[u].push_back(v);
adjbase[v].push_back(u);
}
initdfs(0);
int last=0;
while (!pq.empty()) {
int s=pq.top().second; pq.pop();
last=s;
for (auto u: adjbase[s]) {
unite(u, s);
}
already[s]=true;
}
cout << calcans(last) << endl;
return;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
