#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// Ofast, O0, O1, O2, O3, unroll-loops, fast-math, trapv
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
#define Mp make_pair
#define sep ' '
#define endl '\n'
#define F first
#define S second
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define kill(res) cout << res << '\n', exit(0);
#define set_dec(x) cout << fixed << setprecision(x);
#define fast_io ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io freopen("input.txt", "r", stdin) ; freopen("output.txt", "w", stdout);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll L = 20;
const ll N = 2e5 + 50;
const ll Mod = 1e9 + 7;
int n, p[N], ver[N], h[N], par[N][L], pr[N], sz[N], mxh[N]; ll val[N];
vector<int> adj[N];
void dfs(int v, int p = 0){
par[v][0] = p;
for(int i = 1; i < L; i++){
if(!par[v][i-1]) break;
par[v][i] = par[par[v][i-1]][i-1];
}
for(int u: adj[v]){
if(u == p) continue;
h[u] = h[v] + 1; dfs(u, v);
}
}
int getkth(int v, int k){
for(int i = 0; i < L; i++){
if(k >> i & 1) v = par[v][i];
}
return v;
}
int lca(int u, int v){
if(h[v] < h[u]) swap(u, v);
v = getkth(v, h[v] - h[u]);
if(u == v) return v;
for(int i = L-1; i >= 0; i--){
if(par[v][i] != par[u][i]){
v = par[v][i]; u = par[u][i];
}
}
return par[v][0];
}
int dist(int u, int v){
return (h[u] + h[v] - 2 * h[lca(u, v)]);
}
int getPar(int v){
return (pr[v] == v ? v : pr[v] = getPar(pr[v]));
}
void Union(int u, int v, int a, ll b){
u = getPar(u);
v = getPar(v);
if(u == v) return;
if(sz[v] < sz[u]) swap(u, v);
sz[v] += sz[u];
pr[u] = v;
mxh[v] = a;
val[v] = b;
}
int main(){
fast_io;
cin >> n;
for(int i = 1; i <= n; i++){
cin >> p[i]; ver[p[i]] = i;
}
int u, v;
for(int i = 1; i < n; i++){
cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
dfs(1);
for(int i = 1; i <= n; i++){
pr[i] = i; sz[i] = 1; mxh[i] = p[i];
}
for(int i = 1; i <= n; i++){
v = ver[i];
ll ans = 0;
for(int u: adj[v]){
if(p[u] > p[v]) continue;
int up = getPar(u);
ans = max(ans, val[up] + dist(ver[mxh[up]], v));
}
for(int u: adj[v]){
if(p[u] > p[v]) continue;
Union(u, v, i, ans);
}
if(i == n) cout << ans << endl;
}
}
