#include <bits/stdc++.h>
struct DSU {
std::vector<long long> height;
std::vector<int> boss;
explicit DSU(int N) {
boss.resize(1 + N);
height.resize(1 + N);
for (int i = 1; i <= N; i++)
boss[i] = i;
}
int find(int x) {
if (x == boss[x])
return x;
boss[x] = find(boss[x]);
return boss[x];
}
void merge(int a, int b) {
int sa = find(a);
int sb = find(b);
if (sa > sb)
boss[sb] = sa;
else
boss[sa] = sb;
}
};
struct DistanceCalculator {
int lg = 0;
std::vector<std::vector<int>>& graph;
std::vector<std::vector<int>> parent;
std::vector<int> dep;
DistanceCalculator(std::vector<std::vector<int>>& _graph): graph(_graph) {
int N = (int)graph.size() - 1;
while ((1 << (lg + 1)) <= N)
lg++;
parent.resize(1 + N, std::vector<int>(1 + lg));
dep.resize(1 + N);
predfs();
}
void predfs(int node = 1, int father = 0) {
parent[node][0] = father;
for (int l = 1; l <= lg; l++)
parent[node][l] = parent[parent[node][l - 1]][l - 1];
for (auto it: graph[node]) {
if (it != father) {
dep[it] = dep[node] + 1;
predfs(it, node);
}
}
}
int goup(int node, int x) {
for (int l = lg; l >= 0; --l)
if ((1 << l) & x)
node = parent[node][l];
return node;
}
int lca(int a, int b) {
if (dep[a] > dep[b])
a = goup(a, dep[a] - dep[b]);
else
b = goup(b, dep[b] - dep[a]);
if (a == b) return a;
for (int l = lg; l >= 0; --l)
if (parent[a][l] != parent[b][l]) {
a = parent[a][l];
b = parent[b][l];
}
return parent[a][0];
}
int dist(int a, int b) {
int l = lca(a, b);
return dep[a] + dep[b] - 2 * dep[l];
}
};
int main() {
std::cin.tie(NULL);
std::iostream::sync_with_stdio(false);
int N;
std::cin >> N;
std::vector<int> perm(1 + N);
for (int i = 1; i <= N; i++)
std::cin >> perm[i];
std::vector<std::vector<int>> graph(1 + N);
for (int i = 0; i < N - 1; i++) {
int a, b;
std::cin >> a >> b;
a = perm[a];
b = perm[b];
graph[a].push_back(b);
graph[b].push_back(a);
}
DSU dsu(N);
DistanceCalculator dc(graph);
//std::cerr << dc.dist(2, 3) << "\n";
for (int node = 1; node <= N; node++) {
long long height = 0;
for (auto it: graph[node]) {
if (node > it) {
height = std::max(height, dsu.height[dsu.find(it)] + dc.dist(node, dsu.find(it)));
dsu.merge(node, it);
}
}
dsu.height[dsu.find(node)] = height;
//std::cerr << node << " has height " << height << "\n";
}
std::cout << dsu.height[dsu.find(N)];
return 0;
}
