#include "bits/stdc++.h"
using namespace std;
#define ll long long
#define ln '\n'
const int N = 2e5 + 5;
const int LG = 20;
int n, a[N], par[N], dep[N], up[LG][N];
ll dp[N];
vector<int> adj[N];
void dfs(int u, int p){
dep[u] = 1 + dep[p];
up[0][u] = p;
for (int i = 1; i < LG; i++) up[i][u] = up[i-1][up[i-1][u]];
for (auto v: adj[u]){
if (v == p) continue;
dfs(v, u);
}
}
int lca(int u, int v){
if (dep[u] < dep[v]) swap(u, v);
for (int i = LG-1; i >= 0; i--) if (dep[up[i][u]] >= dep[v]) u = up[i][u];
if (u == v) return u;
for (int i = LG-1; i >= 0; i--){
if (up[i][u] != up[i][v]) u = up[i][u], v = up[i][v];
}
return up[0][u];
}
ll dist(int u, int v) {return dep[u] + dep[v] - (dep[lca(u, v)] * 2);}
int find(int u) {return u == par[u]? u: par[u]=find(par[u]);}
void solve(){
cin >> n;
iota(par, par+n+1, 0);
for (int i = 1; i <= n; i++) cin >> a[i];
for (int i = 0; i < n-1; i++){
int u, v; cin >> u >> v;
u = a[u]; v = a[v];
adj[u].push_back(v);
adj[v].push_back(u);
}
dfs(n, n);
for (int i = 1; i <= n; i++){
for (auto v: adj[i]){
v = find(v);
if (v < i) {
par[v] = i;
dp[i] = max(dp[i], dist(i, v) + dp[v]);
}
}
}
cout << dp[n] << ln;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// int TT; cin >> TT;
// while (TT--) {solve();}
solve();
}
