#include <bits/stdc++.h>
#include <fstream>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/trie_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
template<class A, class B>
ostream& operator<<(ostream& o, const pair<A, B>& p) {return o << '(' << p.first << ", " << p.second << ')';}
template<size_t Index = 0, typename... Types>
ostream& printTupleElements(ostream& o, const tuple<Types...>& t) {if constexpr (Index < sizeof...(Types)){if(Index > 0){o << ", ";}o << get<Index>(t);printTupleElements<Index + 1>(o, t);}return o;}
template<typename... Types>
ostream& operator<<(ostream& o, const tuple<Types...>& t){o << "(";printTupleElements(o, t);return o << ")";}
template<class T>
auto operator<<(ostream& o, const T& x) -> decltype(x.end(), o){o << '{';bool first = true;for (const auto& e : x){if (!first){o << ", ";}o << e;first = false;} return o << '}';}
//#define DEBUG
#ifdef DEBUG
#define fastio()
#define debug(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n'
#define check(x) if (!(x)) { cerr << "Check failed: " << #x << " in line " << __LINE__ << endl; exit(1); }
#else
#define fastio() ios_base::sync_with_stdio(0); cin.tie(0);
#define debug(...)
#define check(x) 
#endif
typedef long long ll;
#define pi pair<int, int>
#define pll pair<ll, ll>
#define st first
#define nd second
#define vi vector<int>
#define vll vector<ll>
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
constexpr int LIM = 2e5;
vi g[LIM + 10];
int tab[LIM + 10];
ll dp[LIM + 10];
int nxt[LIM + 10][19];
int pre[LIM + 10];
int post[LIM + 10];
int oj[LIM + 10];
int mx[LIM + 10];
int aktpre = 1;
int aktpost = 1;
void dfs(int v, int o) {
	pre[v] = aktpre++;
	nxt[v][0] = o;
	for(int i = 1; i <= 18; i++) {
		nxt[v][i] = nxt[nxt[v][i - 1]][i - 1];
	}
	for(auto x : g[v]) {
		if(x != o) {
			dfs(x, v);
		}
	}
	post[v] = aktpost++;
}
bool czy(int a, int b) {
	return pre[a] <= pre[b] && post[a] >= post[b];
}
int dist(int v, int o) {
	if(v == o) {
		return 0;
	}
	if(pre[v] < pre[o]) {
		swap(v, o);
	}
	int ans = 0;
	for(int i = 18; i >= 0; i--) {
		if(!czy(nxt[v][i], o)) {
			ans += (1 << i);
			v = nxt[v][i];
		}
	}
	if(!czy(v, o)) {
		ans++;
		v = nxt[v][0];
	}
	for(int i = 18; i >= 0; i--) {
		if(!czy(nxt[o][i], v)) {
			ans += (1 << i);
			o = nxt[o][i];
		}
	}
	if(!czy(o, v)) {
		ans++;
		o = nxt[o][0];
	}
	return ans;
}
int find(int a) {
	if(oj[a] == a) {
		return a;
	}
	return oj[a] = find(oj[a]);
}
void uni(int a, int b) {
	a = find(a);
	b = find(b);
	oj[a] = b;
	mx[b] = max(mx[b], mx[a]);
}
void solve() {
	//ifstream cin("nazwa.in");
	//ofstream cout("nazwa.out");
	int n;
	cin >> n;
	vector<pi>vs;
	vi pos(n + 1, 0);
	for(int i = 1; i <= n; i++) {
		cin >> tab[i];
		vs.eb(tab[i], i);
		pos[tab[i]] = i;
		mx[i] = tab[i];
		oj[i] = i;
	}
	sort(all(vs));
	for(int i = 1; i < n; i++) {
		int a, b;
		cin >> a >> b;
		g[a].eb(b);
		g[b].eb(a);
	}
	dfs(1, 1);
	for(auto [val, v] : vs) {
		for(auto x : g[v]) {
			if(tab[x] < val) {
				int a = pos[mx[find(x)]];
				dp[v] = max(dp[v], dp[a] + dist(v, a));
				uni(x, v);
			}
		}
		debug(v, dp[v]);
		if(val == n) {
			cout << dp[v] << '\n';
			return;
		}
	}
}
int main() {
	fastio();
	int t = 1;
	//cin >> t;
	while(t--) {
		solve();
	}
}