#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=2e5+5,LOG=20,mod=1e9+7,inf=1e18;
int n,p[N],rp[N],x,y,d[N],dp[N],ans[N],tin[N],tout[N],l[N][LOG],cnt;
vector <int> v[N];
void dfs(int i,int p){
tin[i]=++cnt; l[i][0]=p; dp[i]=dp[p]+1;
for (int j=1; j<LOG; j++)
l[i][j]=l[l[i][j-1]][j-1];
for (int j:v[i]){
if (j==p) continue;
dfs(j,i);
}
tout[i]=cnt;
}
bool ispar(int a,int b){
if (!a || (tin[a]<=tin[b] && tout[a]>=tout[b])) return 1;
return 0;
}
int lca(int a,int b){
if (ispar(a,b)) return a;
for (int j=LOG-1; j>=0; j--)
if (!ispar(l[a][j],b))
a=l[a][j];
return l[a][0];
}
int dist (int a,int b){
return dp[a]+dp[b]-2*dp[lca(a,b)];
}
int par(int i){
if (i==d[i]) return i;
return d[i]=par(d[i]);
}
void make(int a,int b){
a=par(a); b=par(b);
if (a==b) return;
if (p[a]<p[b]) swap(a,b);
d[b]=a;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin>>n;
for (int i=1; i<=n; i++) cin>>p[i],d[i]=i,rp[p[i]]=i;
for (int i=1; i<n; i++){
cin>>x>>y;
v[x].push_back(y);
v[y].push_back(x);
}
dfs(1,0);
for (int i=1; i<=n; i++){
x=rp[i];
for (int j:v[x]){
if (p[j]>i) continue;
// cout << j << ' ' << i << ' ' << x << ' ' << par(j) << ' ' << dist(x, par(j)) << '\n';
ans[x]=max(ans[x],dist(x,par(j))+ans[par(j)]);
make(x,j);
}
// cout << "ans[x] = " << ans[x] << '\n';
}
cout<<ans[rp[n]];
}
