#include <bits/stdc++.h>
#define ar array
//#define int long long
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 2e5 + 5;
struct union_find {
int n;
vector<int> par, size, mx;
union_find(int _n) : n(_n), par(n+1), size(n+1, 1), mx(n+1) {
for(int i=1; i<=n; i++) par[i] = mx[i] = i;
}
int find(int u) {
if(u == par[u]) return u;
return par[u] = find(par[u]);
}
void uni(int a, int b, int M) {
a = find(a); b = find(b);
if(a == b) return ;
if(size[a] < size[b]) swap(a, b);
par[b] = a;
size[a] += size[b];
mx[a] = M;
}
int get(int u) {
return mx[find(u)];
}
};
int n, P[maxn], T[maxn][20], up[maxn][20], dep[maxn];
vector<int> G[maxn];
void dfs(int u, int p) {
for(int i=1; i<20; i++) up[u][i] = up[ up[u][i-1] ][i-1];
for(int v : G[u]) {
if(v == p) continue;
dep[v] = dep[u] + 1;
up[v][0] = u;
dfs(v, u);
}
}
int lca(int a, int b) {
if(dep[a] < dep[b]) swap(a, b);
int d = dep[a] - dep[b];
for(int j=19; j>=0; j--)
if(d & (1 << j)) a = up[a][j];
if(a == b) return a;
for(int j=19; j>=0; j--)
if(up[a][j] != up[b][j]) a = up[a][j], b = up[b][j];
return up[a][0];
}
int dist(int a, int b) {
return dep[a] + dep[b] - 2*dep[lca(a, b)];
}
signed main() {
cin >> n;
for(int i=1; i<=n; i++) cin >> P[i];
for(int i=0; i<n-1; i++) {
int a, b; cin >> a >> b;
G[a].push_back(b);
G[b].push_back(a);
}
dfs(1, 1);
vector<ll> dp(n+1);
vector<pii> ord;
for(int i=1; i<=n; i++) ord.push_back({ P[i], i });
sort(ord.begin(), ord.end());
dp[ord[0].second] = 0;
union_find dsu(n);
for(auto [_, u] : ord) {
// cout << "at " << u << '\n';
for(int v : G[u]) {
if(P[v] > P[u]) continue;
// cout << "to " << v << '\n';
int mx = dsu.get(v);
// cout << "! " << mx << " " << dist(mx, u) << endl;
dp[u] = max(dp[u], dp[mx] + dist(mx, u));
dsu.uni(u, v, u);
}
}
// for(int i=1; i<=n; i++) cout << dp[i] << " ";
// cout << '\n';
cout << dp[ord.back().second] << '\n';
}
