#include <bits/stdc++.h>
#define ar array
//#define int long long
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 2e5 + 5;
int n, P[maxn], T[maxn][20];
vector<int> G[maxn];
int mrg(int i, int j) {
return P[i] > P[j] ? i : j;
}
int query(int l, int r) {
int k = __lg(r-l+1);
return mrg(T[l][k], T[r-(1<<k)+1][k]);
}
ll dnc(int l, int r, int p) {
if(l == r) return 0;
ll ans = 0;
//oj levo
if(p > l) {
int p2 = query(l, p-1);
ans = max(ans, p - p2 + dnc(l, p-1, p2));
}
//oj desno
if(p < r) {
int p2 = query(p+1, r);
ans = max(ans, p2 - p + dnc(p+1, r, p2));
}
return ans;
}
signed main() {
cin >> n;
for(int i=1; i<=n; i++) cin >> P[i];
for(int i=1; i<=n; i++) T[i][0] = i;
for(int j=1; j<20; j++)
for(int i=1; i+(1<<j)-1<=n; i++) T[i][j] = mrg(T[i][j-1], T[i+(1<<(j-1))][j-1]);
for(int i=0; i<n-1; i++) {
int a, b; cin >> a >> b;
G[a].push_back(b);
G[b].push_back(a);
}
cout << dnc(1, n, query(1, n)) << '\n';
}
