#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
#include <map>
#include <stack>
#include <bitset>
#include <string>
#include <cstring>
#include <iterator>
#include <random>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef long double ld;
const ll dim = 1e3+7;
//const ll mod = 1e9 + 7;
const ll inf = 1e17 + 77;
#define endl "\n"
#define fi first
#define pb push_back
#define se second
#define vll vector<ll>
ll n, m;
pll h[dim];
vll a[dim];
ll dp[dim], dep[dim], tin[dim], tout[dim];
ll jump[24][dim];
vll g[dim];
ll boss[dim];
ll findboss(ll v){
if(boss[v]==v)return v;
return boss[v]=findboss(boss[v]);
}
ll t=0;
void dfs(ll v,ll p, ll d){
dep[v]=d;
t++;
tin[v]=t;
jump[0][v]=p;
for(int i=1; i<=21; i++){
jump[i][v]=jump[i-1][jump[i-1][v]];
}
for( auto x:a[v]){
if(x==p)continue;
dfs(x, v, d+1);
}
t++;
tout[v]=t;
}
ll same(ll x, ll y){
if(tin[x]<=tin[y] && tout[y]<=tout[x])return 1;
swap(x, y);
if(tin[x]<=tin[y] && tout[y]<=tout[x])return 1;
return 0;
}
ll lca(ll x, ll y){
if(dep[x]>dep[y])swap(x, y);
ll cur=x;
if(same(x, y)){
return x;
}
for(int st=20; st>=0; st--){
if(!same(jump[st][cur], y)){
cur=jump[st][cur];
}
}
// cout<<cur<<endl;
return jump[0][cur];
}
ll dst(ll x, ll y){
ll p1=dep[lca(x, y)];
return dep[x]+dep[y]-2*p1;
}
void unite(ll x, ll y){
ll xx=findboss(x);
boss[xx]=y;
}
int main() {
ll k, u, v;
string s;
cin>>n;
for(int i=1; i<=n; i++){
cin>>h[i].fi;
h[i].se=i;
dp[i]=0;
boss[i]=i;
}
for(int i=1; i<=n-1; i++){
cin>>u>>v;
a[u].pb(v);
a[v].pb(u);
if(h[u]<h[v])swap(u, v);
g[u].pb(v);
}
sort(h+1, h+1+n);
t=0;
dfs(1, 1, 1);
for(int i=1; i<=n; i++){
ll cur=h[i].se;
// cout<<cur<<" -- ";
for(auto x:g[cur]){
ll tmp=findboss(x);
ll d=dst(cur, tmp);
//cout<<tmp<<" "<<d<<endl;
dp[cur]=max(dp[cur], dp[tmp]+d);
}
// cout<<dp[cur]<<endl;
for(auto x:g[cur]){
unite(x, cur);
}
}
cout<<dp[h[n].se]<<endl;
return 0;
}
