#include <bits/stdc++.h>
#define fst first
#define snd second
#define pb push_back
#define SZ(x) (int)x.size()
#define ALL(x) x.begin(),x.end()
#define forn(i,a,b) for(int i = a; i<b; i++)
#define mset(a,v) memset(a,v,sizeof(a))
#define FIN ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
typedef long long ll;
const int MAXN = 200000+5;
#ifdef D
#define debug(x) cout << x
#else
#define debug(x) //nothing
#endif
ll n;
ll p[MAXN];
ll res[MAXN];
vector<ll> adj[MAXN];
ll toJ;
ll lvlToJ;
void dfs(ll nd , ll pa , ll val , ll lvl){
for(auto i:adj[nd]) if(i!=pa){
if(p[i]>val){
if(toJ==-1 || p[toJ]>p[i]){
toJ=i;
lvlToJ=lvl+1;
}
continue;
}
dfs(i,nd,val,lvl+1);
}
}
int main(){
mset(res,0);
cin>>n;
forn(i,0,n) cin>>p[i];
ll u,v;
forn(i,0,n-1){
cin>>u>>v; u--; v--;
adj[u].pb(v);
adj[v].pb(u);
}
vector<pair<ll,ll>> ord;
forn(i,0,n){
ord.pb({p[i],i});
}
sort(ALL(ord));
forn(i,0,n-1){
toJ=-1;
lvlToJ=-1;
ll nd = ord[i].snd;
ll val = ord[i].fst;
dfs(nd,-1,val,0);
debug(i<<" "<<nd<<" "<<toJ<<" "<<lvlToJ<<'\n');
debug(res[nd]<<'\n');
res[toJ]=max(res[toJ], res[nd]+lvlToJ);
}
cout<<res[ord.back().snd]<<'\n';
return 0;
}
