#include<bits/stdc++.h>
typedef long long ll;
#define pb push_back
#define fr first
#define sc second
using namespace std;
int n;
int val[200023],loc[200023];
vector<int>komsu[200023];
int dep[200023],eu[200023];
int tim=0;
int spar[400023][19],lg[400023];
int from[200023];
ll dp[200023];
vector<int>v;
void dfs(int pos){
spar[++tim][0]=pos;
eu[pos]=tim;
for(int x:komsu[pos]){
if(eu[x])continue;
dep[x]=dep[pos]+1;
dfs(x);
spar[++tim][0]=pos;
}
}
int query(int l,int r){
int a=spar[l][lg[r-l+1]],b=spar[r-(1<<lg[r-l+1])+1][lg[r-l+1]];
if(dep[a]<dep[b])return a;
return b;
}
int lca(int a,int b){
if(eu[a]>eu[b])swap(a,b);
return query(eu[a],eu[b]);
}
bool on_path(int a,int b,int c){
int ab=lca(a,b),bc=lca(b,c),ac=lca(a,c);
if(dep[c]<dep[ab])return false;
if(bc==c||ac==c)return true;
return false;
}
int dis(int a,int b){
return dep[a]+dep[b]-2*dep[lca(a,b)];
}
void cal(){
int m=v.back();
v.clear();
queue<int>q;
for(int i=1;i<m;i++){
from[loc[i]]=0;
}
for(int i=m;i<=n;i++){
q.push(loc[i]);
while(q.size()){
int pos=q.front();
q.pop();
if(loc[i]!=pos)from[pos]=loc[i];
for(int x:komsu[pos]){
if(val[x]>=i)continue;
if(from[x])continue;
q.push(x);
}
}
}
}
int main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);
cin>>n;
for(int i=2;i<=n*2;i++){
lg[i]=lg[i/2]+1;
}
for(int i=1;i<=n;i++){
cin>>val[i];
loc[val[i]]=i;
}
for(int i=1;i<n;i++){
int x,y;cin>>x>>y;
komsu[x].pb(y);
komsu[y].pb(x);
}
dfs(1);
for(int i=1;i<19;i++){
for(int j=1;j+(1<<i)-1<=tim;j++){
spar[j][i]=spar[j][i-1];
int x=spar[j+(1<<(i-1))][i-1];
if(dep[x]<dep[spar[j][i]])spar[j][i]=x;
}
}
v.pb(n);
ll ans=0;
cal();
for(int i=n-1;i>=1;i--){
if(int(v.size())*int(v.size())>=n){
cal();
}
for(int j=0;j<v.size();j++){
if((!on_path(loc[i],loc[v[j]],from[loc[i]]))&&(!on_path(loc[i],loc[v[j]],from[loc[v[j]]]))){
from[loc[i]]=loc[v[j]];
}
}
dp[loc[i]]=dp[from[loc[i]]]+dis(loc[i],from[loc[i]]);
v.pb(i);
ans=max(ans,dp[loc[i]]);
}
cout<<ans;
}
