#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define f first
#define s second
#define all(x) x.begin(),x.end()
const int mxn=2e5+5;
int num[mxn];
pair<int,int> table[20][mxn];
ll cal(int l,int r){
if(l==r) return 0;
int p=__lg(r-l+1);
int node=max(table[p][l],table[p][r+1-(1<<p)]).s;
int leftnode=-1,rightnode=-1;
if(node>l){
p=__lg(node-l);
leftnode=max(table[p][l],table[p][node-(1<<p)]).s;
}
if(node<r){
p=__lg(r-node);
rightnode=max(table[p][node+1],table[p][r+1-(1<<p)]).s;
}
//cout<<l<<' '<<r<<' '<<leftnode<<' '<<node<<' '<<rightnode<<'\n';
if(leftnode!=-1 and rightnode!=-1){
return max(cal(l,node-1)+1ll*(node-leftnode),cal(node+1,r)+1ll*(rightnode-node));
}
else if(leftnode!=-1){
return cal(l,node-1)+1ll*(node-leftnode);
}
else{
return cal(node+1,r)+1ll*(rightnode-node);
}
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n;
cin>>n;
for(int i=0;i<n;i++){
cin>>num[i];
table[0][i]={num[i],i};
num[i]--;
}
for(int i=0;i<n-1;i++){
int a,b;
cin>>a>>b;
}
for(int i=1;i<20;i++){
for(int j=0;j+(1<<i)<=n;j++){
table[i][j]=max(table[i-1][j],table[i-1][j+(1<<(i-1))]);
}
}
cout<<cal(0,n-1)<<'\n';
}
