#include "bits/stdc++.h"
using namespace std;
#define pb push_back
#define endl "\n"
#define int long long
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()
const int N = 2e5 + 10;
const int LOG = 20;
int lift[N][LOG];
int depth[N];
int ar[N];
vector<int> v[N];
vector<array<int,2>> v2[N];
void dfs(int c,int p,int d){
depth[c]=d;
lift[c][0]=p;
for(int i=1;i<LOG;i++) lift[c][i]=lift[lift[c][i-1]][i-1];
for(int x:v[c]){
if(x==p) continue;
dfs(x,c,d+1);
}
}
int kth_par(int a,int x){
for(int i=0;i<LOG;i++) if(x>>i&1) a=lift[a][i];
return a;
}
int lca(int a,int b){
if(depth[a]<depth[b]) swap(a,b);
a=kth_par(a,depth[a]-depth[b]);
if(a==b) return a;
for(int i=LOG-1;i>=0;i--){
if(lift[a][i]!=lift[b][i]){
a=lift[a][i];
b=lift[b][i];
}
}
return lift[a][0];
}
int dist(int a,int b){
return depth[a] + depth[b] - 2*depth[lca(a,b)];
}
int par[N];
int siz[N];
int val[N];
int find(int a){
if(a==par[a]) return a;
return par[a]=find(par[a]);
}
void merge(int a,int b){
a=find(par[a]),b=find(par[b]);
if(a==b) return;
if(siz[a]>siz[b]) swap(a,b);
siz[b]+=siz[a];
par[a]=b;
if(ar[val[a]]>ar[val[b]]) val[b]=val[a];
}
int dp[N];
void dfs2(int c,int p){
for(auto x:v2[c]){
if(x[1]==p) continue;
dfs2(x[1],c);
dp[c]=max(dp[c],x[0]+dp[x[1]]);
}
// cout << "c: " << c << " " << dp[c] << endl;
}
void solve(){
int n;
cin >> n;
for(int i=1;i<=n;i++) cin >> ar[i];
int xd[n+1];
vector<int> act(n+1,0);
for(int i=1;i<=n;i++) xd[ar[i]]=i;
for(int i=1;i<n;i++){
int a,b;
cin >> a >> b;
v[a].pb(b);
v[b].pb(a);
}
for(int i=1;i<=n;i++){
val[i]=i;
siz[i]=1;
par[i]=i;
}
dfs(1,0,0);
for(int i=1;i<=n;i++){
int u = xd[i];
act[u] = 1;
for(int x:v[u]){
if(!act[x]) continue;
int w = val[find(x)];
v2[u].pb({dist(u,w),w});
v2[w].pb({dist(u,w),u});
// cout << "new: " << u << " " << w << " " << dist(u,w) << endl;
}
for(int x:v[u]){
if(!act[x]) continue;
merge(x,u);
}
}
dfs2(xd[n],0);
cout << dp[xd[n]] << endl;
}
int32_t main(){
cin.tie(0); ios::sync_with_stdio(0);
int t=1;//cin >> t;
while(t--) solve();
return 0;
}
