#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
#pragma optimize("g", on)
#pragma GCC optimize("03")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,avx2,mmx,fma,avx,tune=native")
#define int long long
#define all(x) x.begin(),x.end()
#define F first
#define S second
using namespace std;
// using namespace __gnu_pbds;
// #define ordered_set tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update>
const int LG = 20,N = 2e5+1,inf = 1e18,MOD = 998244353;
const double eps = 1e-9;
int T;
vector<int> g[N];
int h[N];
int block[N],dep[N];
void calc(int v,int p){
for(int to:g[v]){
if(to==p) continue;
dep[to]=dep[v]+1;
calc(to,v);
}
}
int get(int v,int p){
int mx=v;
for(int to:g[v]){
if(block[to] || to==p) continue;
int go=get(to,v);
if(h[mx]<h[go]) mx=go;
}
return mx;
}
int dfs(int v,int p){
int res=0;
block[v]=1;
for(int to:g[v]){
if(block[to] || to==p) continue;
int go=get(to,v);
res=max(res,dfs(go,v)+abs(dep[v]-dep[go]));
}
return res;
}
void solve() {
int n;
cin>>n;
int s=0;
for(int i=1;i<=n;i++){
cin>>h[i];
if(h[i]==n) s=i;
}
for(int i=1;i<n;i++){
int u,v;
cin>>u>>v;
g[u].push_back(v);
g[v].push_back(u);
}
calc(s,s);
cout<<dfs(s,s);
return;
}
signed main() {
// freopen("deleg.in","r",stdin);
// freopen("deleg.out","w",stdout);
SS
int t = 1;
if (T) {
cin >> t;
}
while (t--) {
solve();
}
}
/*
*/
