#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define rep(i,a,b) for (int i = a; i <= b; i++)
#define per(i,a,b) for (int i = a; i >= b; i--)
#define fi first
#define se second
#define pii pair<int,int>
#define pb push_back
const int MAXN = 2e5+10;
const int INF = 1e18 + 5;
vector<int> g[MAXN];
int a[MAXN],rp[MAXN],sz[MAXN], mx[MAXN], inv[MAXN], val[MAXN], dep[MAXN], anc[MAXN][31];
int find(int x) {
if (rp[x] == x) return x;
return rp[x] = find(rp[x]);
}
void join(int x, int y) {
x = find(x), y = find(y);
if (x==y)return;
if (sz[x] > sz[y]) swap(x,y);
rp[x] = y;
if(a[mx[y]] < a[mx[x]]) mx[y] = mx[x];
sz[y] += sz[x];
}
void dfs(int u, int p = 1) {
anc[u][0] = p;
for (int &v : g[u]) {
if (v==p) continue;
dep[v] = dep[u] + 1;
dfs(v,u);
}
}
int getu(int u, int jmp) {
int ans = u, cur = 0;
while (jmp > 0) {
if (jmp&1) ans = anc[ans][cur];
cur++;
jmp/=2;
}
return ans;
}
int dist(int u, int v) {
if (dep[u] < dep[v]) swap(u,v);
int lu = u, lv = v;
lu = getu(lu,dep[u]-dep[v]);
per(k,30,0) {
if (anc[lu][k] != anc[lv][k]) {
lu = anc[lu][k];
lv = anc[lv][k];
}
}
if(lu!=lv) lu = anc[lu][0];
return dep[u] + dep[v] - 2*dep[lu];
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(nullptr);
int n; cin >> n;
rep(i,1,n) {
cin >> a[i];
inv[a[i]] = i;
}
rep(i,1,n) rp[i] = i, sz[i] = 1, mx[i] = i;
rep(i,1,n-1) {
int u,v;cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
dfs(1);
rep(k,1,30) {
rep(i,1,n) {
anc[i][k] = anc[anc[i][k-1]][k-1];
}
}
rep(i,1,n) {
int x = inv[i];
for (int &v : g[x]) {
if (a[v] > i) continue;
val[x] = max(val[x], dist(x,mx[find(v)]) + val[mx[find(v)]]);
join(x,v);
}
}
cout << val[inv[n]] << '\n';
return 0;
}
