#include "bits/stdc++.h"
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// https://codeforces.com/blog/entry/79148
class Timer: chrono::high_resolution_clock {
const time_point start_time;
public:
Timer(): start_time(now()) {}
rep elapsed_time() const {
return chrono::duration_cast<chrono::milliseconds>(now() - start_time).count();
}
} timer;
struct DSU {
int n;
vector<int> p, sz, ma;
DSU(vector<int> a) {
n = a.size() - 1;
ma = a;
p.resize(n + 1);
iota(p.begin(), p.end(), 0);
sz.resize(n + 1, 1);
}
int root(int a) {
if (p[a] != a) {
p[a] = root(p[a]);
}
return p[a];
}
void join(int a, int b) {
a = root(a);
b = root(b);
if (sz[a] > sz[b]) {
swap(a, b);
}
p[a] = b;
sz[b] += sz[a];
ma[b] = max(ma[b], ma[a]);
}
};
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, cur = 0;
cin >> n;
vector<int> a(n + 1), l(n + 1), rev(n + 1), dist(n + 1, 0), dp(n + 1, 0);
for (int i = 1; i <= n; i++) {
cin >> a[i];
rev[a[i]] = i;
}
vector<vector<int>> tree(n + 1), up(n + 1);
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
tree[u].push_back(v);
tree[v].push_back(u);
}
auto dfs = [&] (auto self, int c, int p)->void {
if (p) {
int u = p, pos = 0;
while (true) {
up[c].push_back(u);
if (pos >= up[u].size()) {
break;
}
u = up[u][pos];
pos++;
}
}
l[c] = cur;
for (auto &v : tree[c]) {
if (v != p) {
cur++;
dist[v] = dist[c] + 1;
self(self, v, c);
}
}
};
auto lca = [&] (int u, int v) {
if (u == v) {
return u;
}
if (l[u] > l[v]) {
swap(u, v);
}
int c = v;
while (l[c] > l[u]) {
if (l[up[c][0]] <= l[u]) {
c = up[c][0];
}
else {
for (int i = up[c].size() - 1; i >= 0; i--) {
if (l[up[c][i]] > l[u]) {
c = up[c][i];
break;
}
}
}
}
return c;
};
dfs(dfs, 1, 0);
DSU dsu(a);
for (int i = 1; i <= n; i++) {
int u = rev[i];
for (auto &v : tree[u]) {
if (a[v] < i) {
int x = dsu.ma[dsu.root(v)];
dp[u] = max(dp[u], dp[rev[x]] + dist[u] + dist[rev[x]] - 2 * dist[lca(u, rev[x])]);
dsu.join(u, v);
}
}
}
cout << dp[rev[n]];
return 0;
}
