#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define sp << " " <<
#define all(x) x.begin(),x.end()
#define big(x) ((int)(x.size()))
using namespace std;
const int MOD = 1e9+7, LIM = 1e6+1, inf = 2e18;
const int N = 2e5+1;
vi edges[N],tin(N),tout(N),d(N);
int up[N][20];
int timer = 1;
void dfs(int node,int p,int der = 0) {
d[node] = der;
tin[node] = timer++;
up[node][0] = p;
for (int i=1;i<20;i++) up[node][i] = up[up[node][i-1]][i-1];
for (auto it : edges[node]) {
if (it == p) continue;
dfs(it,node,der+1);
}
tout[node] = timer-1;
}
bool anc(int a,int b) {
return tin[a] <= tin[b] && tout[a] >= tout[b];
}
int lca(int a,int b) {
if (anc(a,b)) return a;
if (anc(b,a)) return b;
for (int i = 19;i>=0;i--) {
if (!anc(up[a][i],b)) a = up[a][i];
}
return up[a][0];
}
int dist(int a,int b) {
return d[a]+d[b]-2*d[lca(a,b)];
}
struct DSU {
vi dad;
DSU(int nn) {
dad.resize(nn+1);
iota(all(dad),0ll);
}
int find(int x) {
if (x == dad[x]) return x;
return dad[x] = find(dad[x]);
}
void unite(int x,int y) {
dad[find(x)] = find(y);
}
};
void solve() {
int n;
cin >> n;
vi a(n+1);
for (int i=1;i<=n;i++) cin >> a[i];
for (int i=1;i<=n-1;i++) {
int a,b;
cin >> a >> b;
edges[a].push_back(b);
edges[b].push_back(a);
}
dfs(1,1);
DSU dsu(n);
vi ord(n+1);
iota(all(ord),0ll);
sort(1+all(ord),[&](int x,int y) {
return a[x] < a[y];
});
vi dp(n+1,0);
for (int i=1;i<=n;i++) {
int node = ord[i];
int mx = 0;
for (auto it : edges[node]) {
if (a[it] > a[node]) continue;
//cout << node sp dsu.find(it) sp dist(dsu.find(it),node) << '\n';
mx = max(mx,dist(dsu.find(it),node)+dp[dsu.find(it)]);
}
dp[node] = mx;
for (auto it : edges[node]) {
if (a[it] > a[node]) continue;
dsu.unite(it,node);
}
}
cout << dp[ord[n]] << '\n';
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef Dodi
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
