#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
const int N = 200000;
int aa[N], ii[N], dd[N], pp[N], qq[N], ds[N], rr[N], xx[N];
vector<int> ej[N];
int dfs0(int p, int i, int d) {
dd[i] = d++, pp[i] = p;
int s = 1, j_ = -1, k_ = 0;
for (int j : ej[i])
if (j != p) {
int k = dfs0(i, j, d);
s += k;
if (k_ < k)
j_ = j, k_ = k;
}
qq[i] = j_;
return s;
}
void dfs1(int p, int i, int q) {
int j_ = qq[i]; qq[i] = q;
for (int j : ej[i])
if (j != p)
dfs1(i, j, j == j_ ? q : j);
}
int lca(int i, int j) {
while (qq[i] != qq[j])
if (dd[qq[i]] > dd[qq[j]])
i = pp[qq[i]];
else
j = pp[qq[j]];
return dd[i] < dd[j] ? i : j;
}
int dist(int i, int j) {
return dd[i] + dd[j] - dd[lca(i, j)] * 2;
}
int find(int i) {
return ds[i] < 0 ? i : (ds[i] = find(ds[i]));
}
void join(int i, int j) {
i = find(i);
j = find(j);
if (i == j)
return;
if (ds[i] == ds[j])
ds[i]--;
if (ds[i] < ds[j])
swap(i, j);
ds[i] = j;
if (aa[rr[j]] < aa[rr[i]])
rr[j] = rr[i];
}
int main() {
ios_base::sync_with_stdio(false), cin.tie(NULL);
int n; cin >> n;
for (int i = 0; i < n; i++)
cin >> aa[i], ii[--aa[i]] = i;
for (int h = 0; h < n - 1; h++) {
int i, j; cin >> i >> j, i--, j--;
ej[i].push_back(j);
ej[j].push_back(i);
}
dfs0(-1, 0, 0);
dfs1(-1, 0, 0);
for (int i = 0; i < n; i++)
ds[i] = -1, rr[i] = i;
for (int a = 0; a < n; a++) {
int i = ii[a], x = 0;
for (int j : ej[i])
if (aa[j] < a) {
int r = rr[find(j)];
x = max(x, xx[r] + dist(i, r));
join(i, j);
}
xx[i] = x;
}
cout << xx[ii[n - 1]] << '\n';
return 0;
}
