#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 2e5 + 25;
const int B = 19;
typedef long long ll;
int a[MAXN], n;
vector <int> adj[MAXN];
struct DSU {
int par[MAXN];
void init () {
for (int i = 1; i <= n; i++) {
par[i] = i;
}
}
int find (int x) {
return par[x] == x ? x : par[x] = find(par[x]);
}
void merge (int x, int y) {
x = find(x); y = find(y);
if (x == y) return;
if (a[x] > a[y]) {
par[y] = x;
} else {
par[x] = y;
}
}
} cur;
vector <int> adj2[MAXN];
int dp[B][MAXN], dep[MAXN];
int jump (int x, int y) {
for (int i = B - 1; i >= 0; i--) {
if (y & (1 << i)) {
x = dp[i][x];
}
}
return x;
}
int lca (int x, int y) {
if (dep[x] > dep[y]) swap(x, y);
y = jump(y, dep[y] - dep[x]);
if (x == y) return x ;
for (int i = B - 1; i >= 0; i--) {
if (dp[i][x] != dp[i][y]) {
x = dp[i][x], y = dp[i][y];
}
}
return dp[0][x];
}
ll dist (int x, int y) {
return dep[x] + dep[y] - 2 * dep[lca(x, y)];
}
ll dfs (int pos) {
if (adj2[pos].empty()) return 0;
ll mx = 0;
for (auto j : adj2[pos]) {
mx = max(mx, dist(j, pos) + dfs(j));
}
return mx;
}
void dfs2 (int pos, int par) {
for (auto j : adj[pos]) {
if (j != par) {
dp[0][j] = pos;
for (int i = 1; i < B; i++) {
dp[i][j] = dp[i - 1][dp[i - 1][j]];
}
dep[j] = 1 + dep[pos];
dfs2(j, pos);
}
}
}
void solve () {
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
for (int i = 1; i < n; i++) {
int x, y; cin >> x >> y;
adj[x].push_back(y);
adj[y].push_back(x);
}
dfs2(1, 0);
vector <int> ii;
for (int i = 1; i <= n; i++) {
ii.push_back(i);
}
sort(ii.begin(), ii.end(), [&] (int x, int y) {
return a[x] < a[y];
});
cur.init();
for (auto i : ii) {
for (auto j : adj[i]) {
if (a[j] > a[i]) {
continue;
}
adj2[i].push_back(cur.find(j));
cur.merge(i, cur.find(j));
}
}
int root = -1;
for (int i = 1; i <= n; i++) {
if (a[i] == n) {
root = i;
}
}
cout << dfs(root) << '\n';
}
signed main () {
ios::sync_with_stdio(0); cin.tie(0);
int tc = 1; //cin >> tc;
while (tc--) solve();
}
