#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<long long, null_type, less_equal<>,
rb_tree_tag, tree_order_statistics_node_update>
ordered_set;
#define ll long long
#define ii pair<ll,ll>
#ifndef DEBUG
#define cerr if (0) cerr
#define endl '\n'
#endif
const ll inf=1e15;
const ll maxn=2e5+5;
const ll mod=1e9+7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll arr[maxn];
ii brr[maxn];
ll par[maxn];
ll dp[maxn];
ll root(ll x){
if (par[x]==x) return x;
return par[x]=root(par[x]);
}
void connect(ll a, ll b){
a=root(a),b=root(b);
if (arr[a]>arr[b]) swap(a,b);
par[a]=b;
}
vector<ll> adj[maxn];
ll twok[maxn][22];
ll depth[maxn];
void dfs(ll x, ll p){
twok[x][0]=p;
depth[x]=depth[p]+1;
for (int i=1;i<21;i++){
ll h=twok[x][i-1];
twok[x][i]=twok[h][i-1];
}
for (auto u:adj[x]){
if (u==p) continue;
dfs(u,x);
}
}
ll lca(ll a, ll b){
if (depth[a]<depth[b]) swap(a,b);
for (int i=21;i>=0;i--){
if (depth[twok[a][i]]>=depth[b]) a=twok[a][i];
}
if (a==b) return a;
for (int i=21;i>=0;i--){
if (twok[a][i]!=twok[b][i]) a=twok[a][i],b=twok[b][i];
}
return twok[a][0];
}
ll dis(ll a, ll b){
return depth[a]+depth[b]-2*depth[lca(a,b)];
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n;
cin>>n;
for (int i=1;i<=n;i++){
cin>>arr[i];
brr[i].first=arr[i],brr[i].second=i;
par[i]=i;
}
sort(brr+1,brr+1+n);
ll a,b;
for (int i=1;i<n;i++){
cin>>a>>b;
adj[a].emplace_back(b);
adj[b].emplace_back(a);
}
dfs(1,0);
for (ll i=1;i<=n;i++){
ll x=brr[i].second;
for (auto u:adj[x]){
if (arr[u]<arr[x]){
ll u2=root(u);
dp[x]=max(dp[x],dp[u2]+dis(x,u2));
connect(u2,x);
}
}
}
cout<<dp[brr[n].second];
return 0;
}
