#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 2e5 + 5;
int n;
int a[N], pa[N], sz[N], hv[N], lv[N], hd[N], ord[N], fa[N];
vector<int> adj[N];
long long dp[N];
void dfs(int u,int p = 0){
pa[u] = p;
sz[u] = 1;
lv[u] = lv[p] + 1;
for(auto v : adj[u])
if(v != p){
dfs(v,u);
sz[u]+=sz[v];
if(sz[v]>sz[hv[u]])hv[u]=v;
}
}
void hld(int u,int p=0){
if(!hd[u])hd[u]=u;
if(hv[u])hd[hv[u]]=hd[u],hld(hv[u],u);
for(auto v:adj[u])if(v!=p&&v!=hv[u])hld(v,u);
}
int lca(int u,int v){
while(hd[u]!=hd[v]){
if(lv[hd[u]]<lv[hd[v]])swap(u,v);
u=pa[hd[u]];
}
return lv[u]<lv[v]?u:v;
}
int dist(int u,int v){
return lv[u]+lv[v]-2*lv[lca(u,v)];
}
int fp(int u){
return fa[u]=fa[u]==u?u:fp(fa[u]);
}
signed main(){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n;
for(int i=1;i<=n;i++)cin >> a[i];
for(int i=1;i<n;i++){
int u,v;
cin >> u >> v;
adj[u].emplace_back(v);
adj[v].emplace_back(u);
}
dfs(1);
hld(1);
iota(fa+1,fa+n+1,1);
iota(ord+1,ord+n+1,1);
sort(ord+1,ord+n+1,[&](int i,int j){
return a[i]<a[j];
});
for(int i=1;i<=n;i++){
int u=ord[i];
for(auto v:adj[u])if(a[u]>a[v]){
v=fp(v);
dp[u]=max(dp[u],dp[v]+dist(u,v));
fa[v]=u;
}
}
cout << dp[ord[n]];
}
