#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
#define ff first
#define ss second
#define MP make_pair
const int mxk = 22;
const int mxn = 2e5 + 10;
const int inf = 1e9 + 10;
int anc[mxk][mxn], lvl[mxn];
int mxu[mxk][mxn], h[mxn], n;
vector<int> adj[mxn];
void dfs(int u, int par = 0) {
lvl[u] = lvl[par] + 1;
for(int v : adj[u]) {
if(v == par) continue;
dfs(v, u);
anc[0][v] = u;
mxu[0][v] = max(u, v);
}
}
int path(int u, int v) {
int mx = 0, len = 0;
int sussy = max(u, v);
if(lvl[u] < lvl[v]) swap(u, v);
int jump = lvl[u] - lvl[v];
for(int k = 0; k < mxk; k++) {
if(jump & (1 << k)) {
jump ^= (1 << k);
len += (1 << k);
mx = max(mx, mxu[k][u]);
u = anc[k][u];
}
}
if(mx > sussy) return -inf;
if(u == v) return len;
for(int k = mxk - 1; k >= 0; k--)
if(anc[k][u] != anc[k][v]) {
mx = max(mx, mxu[k][u]);
mx = max(mx, mxu[k][v]);
len += (1 << (k + 1));
u = anc[k][u];
v = anc[k][v];
}
mx = max(mx, anc[0][u]);
if(mx > sussy) return -inf;
return len + 2;
}
int dp[mxn];
void solve() {
cin >> n;
for(int i = 1; i <= n; i++)
cin >> h[i];
for(int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
u = h[u], v = h[v];
adj[u].push_back(v);
adj[v].push_back(u);
}
dfs(n);
for(int k = 1; k < mxk; k++)
for(int i = 1; i <= n; i++) {
int j = anc[k - 1][i];
int m = mxu[k - 1][i];
anc[k][i] = anc[k - 1][j];
mxu[k][i] = max(m, mxu[k - 1][j]);
}
int ans = 0;
for(int i = n - 1; i >= 1; i--) {
// cout << i << endl;
for(int j = i + 1; j <= n; j++) {
dp[i] = max(dp[i], dp[j] + path(i, j));
// cout << j << ' ' << dp[j] << ' ' << path(i, j) << endl;
}
// cout << i << ": " << dp[i] << endl;
ans = max(ans, dp[i]);
}
cout << ans << endl;
}
signed main() {
#ifdef LOCAL
auto start = chrono::high_resolution_clock::now();
#endif
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
signed t = 1; // cin >> t;
while(t--) solve();
#ifdef LOCAL
auto end = chrono::high_resolution_clock::now();
cout << "\n"; for(int i = 0; i <= 20; ++i) cout << '-';
cout << "\nExecution time: " << chrono::duration_cast<chrono::milliseconds> (end - start).count() << "[ms]" << endl;
#endif
return 0;
}
