#include <bits/stdc++.h>
#define int long long
using namespace std;
using idata = vector<int>;
using igrid = vector<idata>;
struct UFD {
idata parents;
UFD (int size) {
parents.resize(size);
iota(parents.begin(), parents.end(), 0);
}
int boss (int x) {
if (parents[x] != x)
parents[x] = boss(parents[x]);
return parents[x];
}
void merge (int a, int b) {
a = boss(a);
b = boss(b);
if (a < b) swap (a, b);
parents[b] = a;
}
};
const int MAXK = 20;
int N;
idata depth;
idata parents;
igrid parents_2k;
igrid roads;
void dfs (int node, int parent, int _depth) {
depth [node] = _depth;
parents [node] = parent;
parents_2k[node][0] = parent;
for (int next : roads[node]) if (next != parent)
dfs(next, node, _depth + 1);
}
void init_lca () {
for (int k = 0; k + 1 < MAXK; k ++) {
for (int i = 0; i < N; i ++) {
if (parents_2k[i][k] == -1) continue ;
parents_2k[i][k + 1]
= parents_2k[parents_2k[i][k]][k];
}
}
}
int jump (int node, int k) {
for (int i = 0; i < MAXK; i ++)
if ((1 << i) & k)
node = parents_2k[node][i];
return node;
}
int lca (int a, int b) {
if (depth[a] > depth[b]) swap(a, b);
b = jump(b, depth[b] - depth[a]);
if (a == b) return a;
for (int i = MAXK - 1; i >= 0; i --) {
if (parents_2k[a][i] == parents_2k[b][i]) continue ;
a = parents_2k[a][i];
b = parents_2k[b][i];
}
return parents[a];
}
int dist (int a, int b) {
int l = lca(a, b);
return depth[a] + depth[b] - 2 * depth[l];
}
idata height;
idata antiheight;
signed main () {
cin >> N;
height.resize(N); antiheight.resize(N);
for (int i = 0; i < N; i ++) {
cin >> height[i]; height[i] --;
antiheight[height[i]] = i;
}
roads.resize(N);
for (int i = 1; i < N; i ++) {
int a, b;
cin >> a >> b;
a --; b --;
roads[a].push_back(b);
roads[b].push_back(a);
}
depth .resize(N);
parents.resize(N);
parents_2k.resize(N, idata(MAXK, -1));
dfs(0, -1, 0);
init_lca();
idata dp(N);
UFD ufd(N);
for (int i = 0; i < N; i ++) {
int pos = antiheight[i];
int mdp = 0;
for (int next : roads[pos]) {
if (height[next] > i) continue ;
int local = ufd.boss(height[next]);
int ldp = dp [antiheight[local]] + dist(antiheight[local], pos);
mdp = max(ldp, mdp);
ufd.merge(i, height[next]);
}
dp[pos] = mdp;
}
cout << dp[antiheight[N - 1]] << endl;
}
