#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int n;
int a[N];
vector <int> ke[N];
int par[N];
namespace sub1 {
int dp[5005];
int dist[5005][5005];
void DFS (int u) {
for (int &v : ke[u]) if (v != par[u]) {
par[v] = u;
DFS(v);
}
}
int find_max (int root, int border, int lim) {
vector <int> vis(n + 2, 0);
vis[root] = vis[border] = true;
queue <int> que;
int max_node = 0;
que.push(root);
while (!que.empty()) {
int u = que.front();
que.pop();
if (a[u] > a[max_node]) max_node = u;
vis[u] = true;
for (int &v : ke[u]) if (!vis[v] && a[v] < lim) {
que.push(v);
}
}
return max_node;
}
int find_max_son (int u, int p, int lim) {
int max_son = u;
for (int &v : ke[u]) {
if (v == p || a[v] > lim) continue;
int choke = find_max_son (v, u, lim);
if (a[choke] > a[max_son]) max_son = choke;
}
return max_son;
}
int dfs (int u, int p) {
if (dp[u] != - 1) return dp[u];
dp[u] = 0;
vector <int> umax;
int s0 = find_max (u, p, a[u]);
if (s0 != - 1 && s0 != u) umax.push_back(s0);
for (int &v : ke[u]) if (a[v] < a[u]) {
int sv = find_max_son (v, u, a[u]);
if (sv != u) umax.push_back(sv);
}
for (int &v : umax) {
dp[u] = max(dp[u], dfs(v, u) + dist[u][v]);
}
return dp[u];
}
void solve () {
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
dist[i][j] = 2e9;
}
queue <int> que;
dist[i][i] = 0;
que.push(i);
while (!que.empty()) {
int u = que.front();
que.pop();
for (int &v : ke[u]) if (dist[i][v] > dist[i][u] + 1) {
dist[i][v] = dist[i][u] + 1;
que.push(v);
}
}
}
int root = max_element(a + 1, a + 1 + n) - a;
DFS(root);
memset(dp, - 1, sizeof dp);
cout << dfs(root, 0);
}
}
namespace sub2 {
long long dp[N];
int lab[N], max_node[N], vis[N];
int P[N][20], h[N];
void dfs (int u) {
for (int &v : ke[u]) if (v != P[u][0]) {
P[v][0] = u;
for (int j = 1; (1 << j) <= n; j++) {
P[v][j] = P[P[v][j - 1]][j - 1];
}
h[v] = h[u] + 1;
dfs(v);
}
}
int LCA (int u, int v) {
if (h[u] < h[v]) swap (u, v);
int z = __lg(h[u]);
for (int s = z; s >= 0; s--) if (h[u] - h[v] >= (1 << s)) u = P[u][s];
if (u == v) return u;
for (int s = z; s >= 0; s--) if (P[u][s] != P[v][s]) u = P[u][s], v = P[v][s];
return P[u][0];
}
int dist (int u, int v) {return h[u] + h[v] - 2 * h[LCA(u, v)];}
int find (int x) {
return lab[x] < 0 ? x : lab[x] = find(lab[x]);
}
bool joint (int u, int v) {
int x = find(u), y = find(v);
if (x == y) return false;
if (lab[x] > lab[y]) swap(x, y);
lab[x]+= lab[y];
lab[y] = x;
if (a[max_node[x]] < a[max_node[y]]) max_node[x] = max_node[y];
return true;
}
void solve () {
for (int i = 1; i <= n; i++) {
lab[i] = - 1;
max_node[i] = i;
}
vector <pair <int, int>> sorted;
for (int i = 1; i <= n; i++) {
sorted.push_back(make_pair(a[i], i));
}
sort(sorted.begin(), sorted.end());
int root = max_element(a + 1, a + 1 + n) - a;
dfs(1);
for (auto x : sorted) {
int u = x.second;
for (int &v : ke[u]) if (vis[v]) {
dp[u] = max(dp[u], dp[max_node[find(v)]] + dist(max_node[find(v)], u));
joint(u, v);
}
vis[u] = 1;
}
cout << dp[root];
}
}
void solve () {
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
for (int i = 1; i < n; i++) {
int u, v; cin >> u >> v;
ke[u].push_back(v); ke[v].push_back(u);
}
sub2 :: solve();
}
signed main () {
ios_base::sync_with_stdio(0); cin.tie(0);
#define kieuoanh "joi23hot4"
if (fopen(kieuoanh".inp", "r")) {
freopen(kieuoanh".inp", "r", stdin); freopen(kieuoanh".out", "w", stdout);
}
solve();
return 0;
}
