#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define ll int
typedef pair<int,int> pi;
typedef pair<ll,ll> pill;
typedef vector <int> vi;
typedef vector <pi> vpi;
typedef pair<pi, ll> pii;
typedef set <ll> si;
typedef long double ld;
#define f first
#define s second
#define mp make_pair
#define FOR(i,s,e) for(int i=s;i<=int(e);++i)
#define DEC(i,s,e) for(int i=s;i>=int(e);--i)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define lbd(x, y) lower_bound(all(x), y)
#define ubd(x, y) upper_bound(all(x), y)
#define aFOR(i,x) for (auto i: x)
#define mem(x,i) memset(x,i,sizeof x)
#define fast ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define INF (ll)1e18
#define MOD 1000000007
typedef pair <vi, int> pvi;
typedef pair <int,pi> ipi;
typedef vector <pii> vpii;
typedef pair <pi,pi> pipi;
#define maxn 500010
int N;
int dp[maxn],A[maxn],B[maxn],best[maxn];
vi adj[maxn];
int p[maxn],twok[maxn][20],depth[maxn];
int fl(int x){
if (p[x] == x) return x;
return p[x] = fl(p[x]);
}
void dfs(int x,int p){
twok[x][0] = p;
FOR(i,1,19){
if (twok[x][i-1] == -1) break;
twok[x][i] = twok[twok[x][i-1]][i-1];
}
aFOR(i, adj[x]) if (i != p){
depth[i] = depth[x] + 1;
dfs(i,x);
}
}
int lca(int a,int b){
if (depth[a] < depth[b]) swap(a,b);
int k = depth[a] - depth[b];
FOR(i,0,19) if (k & (1 << i)){
a = twok[a][i];
}
if (a == b) return a;
DEC(i,19,0) if (twok[a][i] != twok[b][i]){
a = twok[a][i]; b = twok[b][i];
}
return twok[a][0];
}
int d(int a,int b){
int c = lca(a,b);
return depth[a] + depth[b] - 2 * depth[c];
}
int32_t main(){
fast;
cin >> N;
FOR(i,1,N) cin >> A[i];
FOR(i,1,N) B[A[i]] = i;
int a,b;
FOR(i,1,N-1){
cin >> a >> b;
adj[a].pb(b); adj[b].pb(a);
}
mem(twok,-1);
dfs(1,-1);
FOR(i,1,N) p[i] = i;
FOR(i,1,N){
int x = B[i];
aFOR(j, adj[x]) if (A[j] < i){
int opt = fl(j);
dp[x] = max(dp[x],d(opt,x) + dp[opt]);
p[opt] = x;
}
}
cout << dp[B[N]];
}
