#include <bits/stdc++.h>
#define int int64_t
#define pb push_back
using namespace std;
//#define DEBUGGING
#ifdef DEBUGGING
#define debug(x) cout << (#x) << ": " << (x) << endl;
#else
#define debug(x)
#endif
struct Node
{
int head, tail, size, nxt, move_sum, max_node;
Node(int index) : head(index), tail(index), size(1), nxt(-1), move_sum(0), max_node(-1) {}
Node() : Node(-1) {}
};
constexpr static int MXSIZE = 5e5;
constexpr static int MXLOG = 30;
int v[MXSIZE];
array<int,2> sv[MXSIZE];
vector<int> g[MXSIZE];
int bl[MXSIZE][MXLOG];
int depth[MXSIZE];
Node node[MXSIZE];
void dfs(int node, int parent, int d);
void process_bl(int n);
int advance(int node, int steps);
int find_lca(int a, int b);
int get_dist(int a, int b);
void merge(int a, int b);
int32_t main()
{
int n;
cin >> n;
for (int i = 0; i < n; i++) cin >> v[i];
for (int i = 0; i < n-1; i++)
{
int a, b;
cin >> a >> b;
a--,b--;
g[a].pb(b);
g[b].pb(a);
}
dfs(0, 0, 0);
process_bl(n);
for (int i = 0; i < n; i++)
node[i] = Node(i);
for (int i = 0; i < n; i++)
sv[i][0] = v[i], sv[i][1] = i;
sort(sv, sv + n);
for (int j = 0; j < n; j++)
{
int i = sv[j][1];
int best_sum = 0;
for (int c : g[i])
{
if (v[i] > v[c])
{
best_sum = max(best_sum, node[node[c].head].move_sum + get_dist(node[node[c].head].max_node, i));
merge(node[i].head, node[c].head);
}
}
debug(i);
debug(node[i].head);
debug(best_sum);
node[node[i].head].move_sum = best_sum;
node[node[i].head].max_node = i;
}
cout << node[node[0].head].move_sum << "\n";
}
void dfs(int node, int parent, int d)
{
bl[node][0] = parent;
depth[node] = d;
for (int c : g[node])
if (c != parent)
dfs(c, node, d+1);
}
void process_bl(int n)
{
for (int i = 1; i < MXLOG; i++)
for (int j = 0; j < n; j++)
bl[j][i] = bl[bl[j][i-1]][i-1];
}
int advance(int node, int steps)
{
for (int i = 0; i < MXLOG; i++)
if (steps&(1<<i))
node = bl[node][i];
return node;
}
int find_lca(int a, int b)
{
if (depth[a] > depth[b]) swap(a, b);
b = advance(b, depth[b]-depth[a]);
if (a == b) return a;
for (int i = MXLOG-1; i >= 0; i--)
if (bl[a][i] != bl[b][i])
a = bl[a][i], b = bl[b][i];
return bl[a][0];
}
int get_dist(int a, int b)
{
return depth[a] + depth[b] - depth[find_lca(a, b)] * 2;
}
void merge(int a, int b)
{
if (node[b].size > node[a].size) swap(a, b);
node[a].size += node[b].size;
node[node[a].tail].nxt = node[b].head;
node[a].tail = node[b].tail;
while (b != -1)
{
node[b].head = a;
b = node[b].nxt;
}
}
