#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
const int N = 1e5 + 5, LG = 17;
int n;
int a[N], lab[N], top[N], dep[N], pr[LG][N];
long long dp[N];
vector<int> g[N];
void dfs(int u) {
for (int v : g[u]) {
if (v != pr[0][u]) {
pr[0][v] = u;
for (int j = 1; j < LG; ++j) {
pr[j][v] = pr[j - 1][pr[j - 1][v]];
}
dep[v] = dep[u] + 1;
dfs(v);
}
}
}
int lca(int u, int v) {
if (dep[u] < dep[v]) {
swap(u, v);
}
for (int j = LG - 1; ~j; --j) {
if (dep[u] - (1 << j) >= dep[v]) {
u = pr[j][u];
}
}
if (u == v) {
return u;
}
for (int j = LG - 1; ~j; --j) {
if (pr[j][u] != pr[j][v]) {
u = pr[j][u], v = pr[j][v];
}
}
return pr[0][u];
}
int dis(int u, int v) {
return dep[u] + dep[v] - 2 * dep[lca(u, v)];
}
int find(int u) {
return lab[u] < 0 ? u : lab[u] = find(lab[u]);
}
void mrg(int u, int v) {
u = find(u), v = find(v);
if (lab[u] > lab[v]) {
swap(u, v);
swap(top[u], top[v]);
}
lab[u] += lab[v];
lab[v] = u;
}
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
cin >> n;
for (int i = 1; i <= n; ++i) {
cin >> a[i];
}
for (int i = 1; i < n; ++i) {
int u, v; cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
dfs(1);
vector<int> ord(n); iota(ord.begin(), ord.end(), 1);
sort(ord.begin(), ord.end(), [&](int i, int j) {
return a[i] < a[j];
});
iota(top + 1, top + n + 1, 1);
fill(lab + 1, lab + n + 1, -1);
for (int u : ord) {
for (int v : g[u]) {
if (a[v] < a[u]) {
auto x = top[find(v)];
dp[u] = max(dp[u], dp[x] + dis(x, u));
mrg(u, v);
}
}
}
cout << dp[ord.back()];
return 0;
}
