#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
struct dsu{
vector<int> sz, p, m, a;
int n;
dsu(int ns, vector<int>& as){
a = as;
n = ns;
p.resize(n + 1);
sz.resize(n + 1);
m.resize(n + 1);
for (int i = 1; i <= n; i++){
p[i] = m[i] = i;
sz[i] = 1;
}
}
int get(int v){
if (p[v] != v){
p[v] = get(p[v]);
}
return p[v];
}
void unite(int x, int y){
x = get(x); y = get(y);
if (x == y) return;
if (sz[x] > sz[y]){
swap(x, y);
}
p[x] = y;
sz[y] += sz[x];
if (a[m[x]] > a[m[y]]){
m[y] = m[x];
}
}
};
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n; cin>>n;
vector<int> a(n + 1), p(n + 1);
int s = 0;
for (int i = 1; i <= n; i++){
cin>>a[i];
if (a[i] == n){
s = i;
}
p[a[i]] = i;
}
vector<int> g[n + 1];
for (int i = 1; i < n; i++){
int u, v; cin>>u>>v;
g[u].push_back(v);
g[v].push_back(u);
}
dsu T(n + 1, a);
vector<int> tin(n + 1), tout(n + 1), pw[n + 1], d(n + 1);
int lg = ceil(log2(n)), timer = 0;
for (int i = 1; i <= n; i++){
pw[i].resize(lg);
}
function<void(int, int)> fill = [&](int v, int pr){
tin[v] = timer++;
pw[v][0] = pr;
for (int i = 1; i < lg; i++){
pw[v][i] = pw[pw[v][i - 1]][i - 1];
}
for (int i: g[v]){
if (i == pr) continue;
d[i] = d[v] + 1;
fill(i, v);
}
tout[v] = timer++;
};
fill(1, 1);
auto check = [&](int x, int y){
return (tin[x] <= tin[y] && tout[x] >= tout[y]);
};
auto lca = [&](int x, int y){
if (check(x, y)) return x;
if (check(y, x)) return y;
for (int i = lg - 1; i >= 0; i--){
if (!check(pw[x][i], y)){
x = pw[x][i];
}
}
return pw[x][0];
};
auto dist = [&](int x, int y){
return d[x] + d[y] - 2 * d[lca(x, y)];
};
vector<int> f(n + 1);
for (int k = 1; k < n; k++){
int i = p[k];
for (int j: g[i]){
if (a[j] > a[i]) continue;
int v = T.m[T.get(j)];
f[i] = max(f[i], f[v] + dist(i, v));
T.unite(i, j);
}
}
int out = 0;
for (int i = 1; i <= n; i++){
out = max(out, f[i] + dist(i, s));
}
cout<<out<<"\n";
}
