#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
int N; cin >> N;
vector<int> P(N + 1), revP(N + 1);
for(int i = 1; i <= N; i++) cin >> P[i], revP[P[i]] = i;
vector<vector<int>> adj(N + 1);
for(int i = 0; i < N - 1; i++) {
int A, B; cin >> A >> B;
adj[A].push_back(B);
adj[B].push_back(A);
}
vector<vector<int>> jmp(N + 1, vector<int>(20));
vector<int> dep(N + 1);
function<void(int, int)> dfs = [&] (int s, int e) {
jmp[s][0] = e;
dep[s] = dep[e] + 1;
for(int i = 0; i < 19; i++) {
jmp[s][i + 1] = jmp[jmp[s][i]][i];
}
for(int u : adj[s]) if(u != e) dfs(u, s);
};
dfs(1, 0);
auto lca = [&] (int a, int b) {
if(dep[a] < dep[b]) swap(a, b);
for(int i = 19; i >= 0; i--) {
if(dep[jmp[a][i]] >= dep[b])
a = jmp[a][i];
}
if(a == b) return a;
for(int i = 19; i >= 0; i--) {
if(jmp[a][i] != jmp[b][i]) {
a = jmp[a][i];
b = jmp[b][i];
}
}
return jmp[a][0];
};
auto dist = [&] (int s, int t) {
return dep[s] + dep[t] - 2 * dep[lca(s, t)];
};
vector<int> e(N + 1, -1);
function<int(int)> get = [&] (int s) {
return e[s] < 0 ? s : (e[s] = get(e[s]));
};
vector<ll> dp(N + 1);
for(int i = 1; i <= N; i++) {
int s = revP[i];
for(int u : adj[s]) {
if(P[u] <= i) {
int g = get(u);
dp[s] = max(dp[s], dist(s, g) + dp[g]);
e[s] += e[g];
e[g] = s;
}
}
}
cout << dp[revP[N]] << endl;
}
