#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define sz(a) (int)(a.size())
#define all(a) a.begin(),a.end()
#define lb lower_bound
#define ub upper_bound
#define owo ios_base::sync_with_stdio(0);cin.tie(0);
#define debug(...) fprintf(stderr, __VA_ARGS__),fflush(stderr)
#define time__(d) for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false);\
debug("%s time : %.4fs\n", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))
typedef long long int ll;
typedef long double ld;
typedef pair<ll,ll> PII;
typedef pair<int,int> pii;
typedef vector<vector<int>> vii;
typedef vector<vector<ll>> VII;
ll gcd(ll a,ll b){if(!b)return a;else return gcd(b,a%b);}
const int MAXN = 2e5+5;
vector<int>adj[MAXN];
vector<pii>g[MAXN];
int p[MAXN],rp[MAXN],t[4*MAXN],lazy[4*MAXN];
void pushdown(int v){
if(!lazy[v])return;
t[2*v] = lazy[2*v] = t[2*v+1] = lazy[2*v+1] = lazy[v];
lazy[v] = 0;
}
void upd(int v,int l,int r,int tl,int tr,int val){
if(l>r)return;
if(l==tl && r==tr){
t[v] = lazy[v] = val;
return;
}
pushdown(v);
int tm = (tl+tr)/2;
upd(2*v,l,min(r,tm),tl,tm,val);
upd(2*v+1,max(l,tm+1),r,tm+1,tr,val);
t[v] = max(t[2*v],t[2*v+1]);
}
int query(int v,int l,int r,int tl,int tr){
if(l>r)return -1;
if(l==tl && r==tr)return t[v];
pushdown(v);
int tm = (tl+tr)/2;
return max(
query(2*v,l,min(r,tm),tl,tm),
query(2*v+1,max(l,tm+1),r,tm+1,tr));
}
int dep[MAXN],par[MAXN],ded[MAXN];
void dfs(int v){
for(int x:adj[v]){
if(x != par[v]){
par[x] = v;
dep[x] = dep[v]+1;
dfs(x);
}
}
}
int dfs2(int v){
int mx = 0;
for(pii x:g[v]){
mx = max(mx,dfs2(x.fi)+x.se);
}
return mx;
}
int find(int v,int u){
int res = p[v];
for(int x:adj[v]){
if(x==u || ded[x])continue;
res = max(res,find(x,v));
}
return res;
}
void solve(int v,int p){
v = rp[find(v,-1)];
ded[v] = 1;
if(p)g[p].pb({v,abs(dep[v]-dep[p])});
for(int x:adj[v]){
if(ded[x])continue;
solve(x,v);
}
}
int main()
{
owo
int n;
cin>>n;
for(int i=1;i<=n;i++){
cin>>p[i];
rp[p[i]] = i;
}
for(int i=1;i<n;i++){
int v,u;
cin>>v>>u;
adj[v].pb(u);
adj[u].pb(v);
}
dfs(rp[n]);
solve(1,0);
cout<<dfs2(rp[n]);
}
