#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef long double ld;
typedef pair<ll, ll> pll;
#define FOR(i, a, b) for(int i = a; i < b; i++)
#define ROF(i, a, b) for(int i = a; i >= b; i--)
#define ms memset
#define pb push_back
#define fi first
#define se second
const int N = 2e5+1;
vi g[N], d(N); int par[N][18];
void dfs(int u){
for (int v : g[u]){
if (par[u][0]==v) continue;
par[v][0]=u; d[v]=d[u]+1; dfs(v);
}
}
int dist(int U, int V){
int u=U, v=V;
int ans = d[u]+d[v];
if (d[u]<d[v]) swap(u,v);
int len=d[u]-d[v]; int cur=0;
while (len>0){
if (len%2==1) u=par[u][cur];
len/=2; cur++;
}
if (u==v) return ans-2*d[u];
ROF(i,17,0){
if (par[u][i]==par[v][i]) continue;
u=par[u][i]; v=par[v][i];
}
return ans-2*d[u]+2;
}
// DSU
// mx stores vertex with max height
vi h(N), p(N), r(N), mx(N);
int get(int a){
if (p[a]==a) return a;
return p[a]=get(p[a]);
}
void Union(int a, int b){
int c=get(a),d=get(b);
if (c==d) return;
if (r[c]==r[d]) r[c]++;
if (r[c]>r[d]){
p[d]=c;
if (h[mx[d]]>h[mx[c]]) mx[c]=mx[d];
}else{
p[c]=d;
if (h[mx[c]]>h[mx[d]]) mx[d]=mx[c];
}
}
void solve(){
int n; cin>>n;
FOR(i,1,n+1) cin>>h[i];
FOR(i,0,n-1){
int u,v; cin>>u>>v;
g[u].pb(v); g[v].pb(u);
}
par[1][0]=1;
dfs(1);
FOR(j,1,18){
FOR(i,1,n+1){
par[i][j]=par[par[i][j-1]][j-1];
}
}
FOR(i,1,n+1) {p[i]=i; mx[i]=i;}
vii G[n+1];
vii pos(n+1);
FOR(i,1,n+1) pos[i]={h[i],i};
sort(pos.begin(), pos.end());
FOR(i,1,n+1){
int u = pos[i].se;
for (int v : g[u]){
if (h[v]>h[u]) continue;
int w = mx[get(v)];
G[u].pb({w, dist(u,w)});
//cout<<u<<" "<<w<<" "<<dist(u,w)<<"\n";
Union(u,v);
}
}
vector<ll> dis(n+1); vi used(n+1);
queue<int> bfs; bfs.push(pos[n].se);
while (!bfs.empty()){
int u=bfs.front(); bfs.pop(); used[u]=1;
for (ii edge : G[u]){
int v = edge.fi; if (used[v]) continue;
used[v]=1; dis[v]=dis[u]+edge.se;
bfs.push(v);
}
}
ll mx=0; FOR(i,1,n+1) mx=max(mx,dis[i]);
cout<<mx<<"\n";
}
int main(){
ios::sync_with_stdio(false);
if (fopen("input.txt", "r")) {
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
}
int TC = 1;
//cin >> TC;
FOR(i, 1, TC+1){
//cout << "Case #" << i << ": ";
solve();
}
return 0;
}
