#include "bits/stdc++.h"
using namespace std;
const int N=2e5, L=18;
#ifndef LOCAL
#define cerr if(0)cerr
#endif
int n,p[N];
int pp[L][N],d[N];
vector<int>g[N];
long long dp[N];
int f[N];
int uf(int i) { return f[i]==i?i:f[i]=uf(f[i]); }
void dfs(int i){
for(int l=1;l<L;l++)pp[l][i]=pp[l-1][pp[l-1][i]];
for(int j:g[i])if(pp[0][i]!=j){
pp[0][j]=i;
d[j]=d[i]+1;
dfs(j);
}
}
int lca(int i,int j){
if(d[i]<d[j])swap(i,j);
int k=d[i]-d[j];
for(int l=0;l<L;l++)if(k>>l&1)i=pp[l][i];
if(i==j)return i;
for(int l=L-1;l>=0;l--)if(pp[l][i]!=pp[l][j])i=pp[l][i],j=pp[l][j];
return pp[0][i];
}
int dis(int i,int j){return d[i]+d[j]-2*d[lca(i,j)];}
int main() {
cin.tie(0)->sync_with_stdio(0),cin.exceptions(cin.failbit);
cin>>n;
for(int i=0;i<n;i++)cin>>p[i],p[i]--;
for(int h=0;h<n-1;h++){
int i,j;cin>>i>>j,i--,j--;
i=p[i],j=p[j];
cerr<<"edge "<<i<<" "<<j<<endl;
g[i].push_back(j);
g[j].push_back(i);
}
pp[0][0]=0;
dfs(0);
for(int i=0;i<n;i++)f[i]=i;
for(int i=0;i<n;i++){
for(int j:g[i])if(j<i){
int c=uf(j);
cerr<<c<<" "<<i<<"|"<<dis(c,i)<<endl;
dp[i]=max(dp[i],dp[c]+dis(c,i));
f[c]=i;
}
cerr<<"dp["<<i<<"]="<<dp[i]<<endl;
}
cout<<*max_element(dp,dp+n)<<'\n';
}
