#include<bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(false);cin.tie();cout.tie();
#define all(x) x.begin(), x.end()
#define int long long
#define pq priority_queue
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define pp pop_back
#define F first
#define S second
using namespace std;
struct DSU {
int P[200010];
void prep() {
for (int i = 1; i <= 200000; i++) P[i] = i;
}
int find(int x) {return x == P[x] ? x : P[x] = find(P[x]);}
void merge(int x, int y) {
x = find(x);
y = find(y);
P[x] = P[y];
}
} U;
struct GRAPH {
int vis[200010];
int lvl[200010];
int J[200010][20];
vector<int> adj[200010];
void connect(int x, int y) {
adj[x].pb(y);
adj[y].pb(x);
}
void start() {
J[1][0] = 1;
lvl[1] = 0;
dfs(1);
}
void dfs(int s) {
for (int i = 1; i <= 18; i++) J[s][i] = J[J[s][i-1]][i-1];
vis[s] = 1;
for (auto i: adj[s]) {
if (vis[i]) continue ;
lvl[i] = lvl[s] + 1;
J[i][0] = s;
dfs(i);
}
}
int jump(int x, int k) {
for (int i = 17; i >= 0; i--) {
if (k & (1 << i)) x = J[x][i];
}
return x;
}
int LCA(int x, int y) {
if (lvl[x] < lvl[y]) swap(x, y);
x = jump(x, lvl[x] - lvl[y]);
if (x == y) return x;
for (int i = 18; i >= 0; i--) {
if (J[x][i] == J[y][i]) continue ;
x = J[x][i];
y = J[y][i];
}
return J[x][0];
}
int calc(int x, int y) {
int k = LCA(x, y);
return lvl[x] + lvl[y] - 2 * lvl[k];
}
} G;
void solve() {
int n;
cin >> n;
vector<int> h(n);
for (auto &i: h) cin >> i;
for (int i = 1; i < n; i++) {
int x, y;
cin >> x >> y;
x = h[x-1];
y = h[y-1];
G.connect(x, y);
}
G.start();
U.prep();
int ans = 0;
vector<int> mx(n+1, 0);
for (int i = 1; i <= n; i++) {
for (auto j: G.adj[i]) {
if (j > i) continue ;
int x = U.find(j);
mx[i] = max(mx[i], mx[x] + G.calc(i, x));
U.merge(x, i);
}
ans = max(ans, mx[i]);
}
cout << ans << '\n';
}
signed main() {IOS solve(); return 0;}
