// Hallelujah, praise the one who set me free
// Hallelujah, death has lost its grip on me
// You have broken every chain, There's salvation in your name
// Jesus Christ, my living hope
#include <bits/stdc++.h>
using namespace std;
#define REP(i, s, e) for (int i = (s); i < (e); i++)
#define RREP(i, s, e) for (int i = (s); i >= (e); i--)
template <class T>
inline bool mnto(T& a, T b) {return a > b ? a = b, 1 : 0;}
template <class T>
inline bool mxto(T& a, T b) {return a < b ? a = b, 1: 0;}
typedef long long ll;
typedef long double ld;
#define FI first
#define SE second
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
typedef tuple<int, int, int> iii;
#define ALL(_a) _a.begin(), _a.end()
#define SZ(_a) (int) _a.size()
#define pb push_back
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;
typedef vector<iii> viii;
#ifndef DEBUG
#define cerr if (0) cerr
#endif
const int INF = 1000000005;
const ll LINF = 1000000000000000005ll;
const int MAXN = 200005;
const int MAXL = 20;
int n;
int a[MAXN], inv[MAXN];
vi adj[MAXN];
ll dp[MAXN];
int p[MAXL][MAXN], lvl[MAXN];
void dfs(int u) {
REP (k, 1, MAXL) {
if (p[k - 1][u] == -1) {
p[k][u] = -1;
} else {
p[k][u] = p[k - 1][p[k - 1][u]];
}
}
for (int v : adj[u]) {
if (v == p[0][u]) {
continue;
}
lvl[v] = lvl[u] + 1;
p[0][v] = u;
dfs(v);
}
}
int getd(int a, int b) {
if (lvl[a] < lvl[b]) {
swap(a, b);
}
int res = 0;
RREP (k, MAXL - 1, 0) {
if (p[k][a] != -1 && lvl[p[k][a]] >= lvl[b]) {
a = p[k][a];
res += 1 << k;
}
}
if (a == b) {
return res;
}
RREP (k, MAXL - 1, 0) {
if (p[k][a] != p[k][b]) {
res += 1 << k + 1;
a = p[k][a];
b = p[k][b];
}
}
return res + 2;
}
int up[MAXN], rnk[MAXN], mx[MAXN];
void init() {
REP (i, 1, n + 1) {
up[i] = i;
rnk[i] = 1;
mx[i] = a[i];
}
}
int findp(int i) {
if (up[i] == i) return i;
return up[i] = findp(up[i]);
}
void join(int a, int b) {
int pa = findp(a), pb = findp(b);
if (pa == pb) {
return;
}
if (rnk[pa] < rnk[pb]) {
swap(pa, pb);
}
if (rnk[pa] == rnk[pb]) {
rnk[pa]++;
}
up[pb] = pa;
mxto(mx[pa], mx[pb]);
}
int main() {
#ifndef DEBUG
ios::sync_with_stdio(0), cin.tie(0);
#endif
cin >> n;
REP (i, 1, n + 1) {
cin >> a[i];
inv[a[i]] = i;
}
REP (i, 1, n) {
int u, v; cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
p[0][1] = -1;
dfs(1);
init();
REP (i, 1, n + 1) {
int u = inv[i];
cerr << u << '\n';
for (int v : adj[u]) {
if (a[v] > i) {
continue;
}
int j = mx[findp(v)];
int nv = inv[j];
cerr << ' ' << j << ' ' << nv << ' ' << getd(u, nv) << '\n';
mxto(dp[i], dp[j] + getd(u, nv));
join(u, v);
}
}
cout << dp[n] << '\n';
return 0;
}
