#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define pii pair<int,int>
#define pll pair<long long,long long>
#define pb push_back
#define debug(x) cerr<<#x<<"="<<x<<endl
#define pq priority_queue
#define inf 1ll<<60
#define rep(i,a,b) for (ll i=a;i<(b);i++)
#define MP make_pair
#define SZ(x) (int(x.size()))
#define mod 1000000007
#define ALL(x) x.begin(),x.end()
#define endl "\n"
void inc(ll &a,ll b) {a=(a+b)%mod;}
void dec(ll &a,ll b) {a=(a-b+mod)%mod;}
int prod(ll a,ll b) {return ll(a)*ll(b)%mod;}
int lowbit(ll x) {return x&(-x);}
ll p0w(ll base,ll p) {ll ret=1;while(p>0){if (p%2ll==1ll) ret=ret*base%mod;base=base*base%mod;p/=2ll;}return ret;}
const ll maxn=222222;
ll ht[maxn],dep[maxn],up[20][maxn],sz[maxn],fa[maxn];
ll dp[maxn];
vector<ll>alist[maxn];
//dp i is the max distance that cat moves at pillar with height i
void init(){
rep(i,0,maxn)sz[i]=1,fa[i]=i;
}
ll findset(ll u){
if(fa[u]==u)return u;
return fa[u]=findset(fa[u]);
}
bool mergeset(ll u,ll v){
u=findset(u);
v=findset(v);
if(u!=v){
if(sz[u]<sz[v])swap(u,v);
fa[v]=u;
sz[u]+=sz[v];
}
}
void dfs(ll u,ll p){
up[0][u]=p;
for(auto x:alist[u]){
if(x==p)continue;
dep[x]=dep[u]+1;
dfs(x,u);
}
}
ll lca(ll a,ll b){
if(dep[a]<dep[b])swap(a,b);
ll k=dep[a]-dep[b];
rep(i,0,20){
if((1ll<<i)&k)a=up[i][a];
}
if(a==b)return a;
for(ll i=19;i>=0;i--){
if(up[i][a]!=up[i][b]){
a=up[i][a];
b=up[i][b];
}
}
return up[0][a];
}
ll dis(ll a,ll b){
return dep[a]+dep[b]-2*dep[lca(a,b)];
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
//freopen("i.txt","r",stdin);
ll n;cin>>n;
rep(i,1,n+1)cin>>ht[i];
rep(i,1,n){
ll a,b;cin>>a>>b;
alist[ht[a]].pb(ht[b]);
alist[ht[b]].pb(ht[a]);
}
init();
memset(up,-1,sizeof up);
dfs(1,-1);
rep(k,1,20){
rep(i,1,n+1){
if(up[k-1][i]!=-1){
up[k][i]=up[k-1][up[k-1][i]];
}
}
}
rep(i,1,n+1){//iterate all the p values
for(auto x:alist[i]){
x=findset(x);
if(x<i){
fa[x]=i;
dp[i]=max(dp[i],dp[x]+dis(i,x));
}
}
}
cout<<dp[n];
return 0;
}
