/*
Author: Nguyen Chi Thanh - High School for the Gifted - VNU.HCM (i2528)
*/
#include <bits/stdc++.h>
using namespace std;
/* START OF TEMPALTE */
// #define int long long
#define ll long long
#define ull unsigned long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define fi first
#define se second
#define popcount __builtin_popcountll
#define all(x) (x).begin(), (x).end()
#define BIT(x, i) (((x) >> (i)) & 1)
#define MASK(x) (1ll << (x))
#define SZ(a) ((int32_t)a.size())
#define debug(a, l, r) {for (int _i = (l); _i <= (r); ++_i) cout << (a)[_i] << ' '; cout << '\n';}
template<class X, class Y>
bool minimize(X &x, const Y &y) {
if (x > y) {
x = y;
return true;
} else return false;
}
template<class X, class Y>
bool maximize(X &x, const Y &y) {
if (x < y) {
x = y;
return true;
} else return false;
}
/* END OF TEMPALTE */
struct DSU {
int n;
vector<int> par;
DSU(int _n) : n(_n) {
par.resize(n + 5);
iota(all(par), 0);
}
int findSet(int u) {
while (u != par[u])
u = par[u] = par[par[u]];
return u;
}
// x is parent of y
bool unite(int x, int y) {
x = findSet(x);
y = findSet(y);
if (x == y) return 0;
par[y] = x;
return 1;
}
};
const int MAXN = 2e5 + 5;
const int LG = 18;
int n, h[MAXN], pos[MAXN], depth[MAXN], up[LG + 1][MAXN];
ll dp[MAXN];
vector<int> adj[MAXN], g[MAXN];
void init() {
cin >> n;
for (int i = 1; i <= n; ++i) {
cin >> h[i];
pos[h[i]] = i;
}
for (int i = 1; i < n; ++i) {
int u, v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
}
void dfsLCA(int u, int par = 0) {
up[0][u] = par;
for (int j = 1; j <= LG; ++j)
up[j][u] = up[j - 1][up[j - 1][u]];
for (int v : adj[u]) {
if (v == par) continue;
depth[v] = depth[u] + 1;
dfsLCA(v, u);
}
}
int lift(int u, int k) {
for (int j = 0; j <= LG; ++j)
if (BIT(k, j)) u = up[j][u];
return u;
}
int lca(int u, int v) {
if (depth[u] > depth[v]) swap(u, v);
int diff = depth[v] - depth[u];
v = lift(v, diff);
if (u == v) return u;
for (int j = LG; j >= 0; --j) {
if (up[j][u] != up[j][v]) {
u = up[j][u];
v = up[j][v];
}
}
return up[0][u];
}
int dist(int u, int v) {
return depth[u] + depth[v] - 2 * depth[lca(u, v)];
}
void dfsDP(int u, int par = 0) {
for (int v : g[u]) {
if (v == par) continue;
dfsDP(v, u);
maximize(dp[u], dp[v] + dist(u, v));
}
}
void solve() {
dfsLCA(1);
DSU dsu(n);
for (int i = 1; i <= n; ++i) {
int u = pos[i];
for (int v : adj[u]) {
if (h[v] > h[u]) continue;
int to = dsu.findSet(v);
g[u].push_back(to);
dsu.unite(u, to);
}
}
dfsDP(pos[n]);
cout << dp[pos[n]];
}
signed main() {
#ifdef NCTHANH
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(nullptr); cout.tie(nullptr);
init();
solve();
return 0;
}
