#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int long long
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define FORD(i, a, b) for (int i = (b); i >= (a); i --)
#define REP(i, a) for (int i = 0; i < (a); ++i)
#define REPD(i, a) for (int i = (a) - 1; i >= 0; --i)
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
/*
Phu Trong from Nguyen Tat Thanh High School for gifted student
*/
template <class X, class Y>
bool minimize(X &x, const Y &y){
X eps = 1e-9;
if (x > y + eps) {x = y; return 1;}
return 0;
}
template <class X, class Y>
bool maximize(X &x, const Y &y){
X eps = 1e-9;
if (x + eps < y) {x = y; return 1;}
return 0;
}
#define MAX 200005
#define LOG 19
vector<int> G[MAX];
int label[MAX], numNode;
int root = 1;
int up[MAX][LOG], depth[MAX];
void pre_dfs(int u, int p = -1){
for (int &v : G[u]) if(v ^ p){
up[v][0] = u;
depth[v] = depth[u] + 1;
for (int i = 1; i < LOG; ++i) up[v][i] = up[up[v][i - 1]][i - 1];
pre_dfs(v, u);
}
}
int low_bit(int p){
return (p & (-p));
}
int lca(int u, int v){
if (depth[u] < depth[v]) swap(u, v);
int dis = depth[u] - depth[v];
for (; dis > 0; dis ^= low_bit(dis)){
int i = __builtin_ctz(low_bit(dis));
u = up[u][i];
}
if(u == v) return u;
for (int i = LOG - 1; i >= 0; --i) if(up[u][i] != up[v][i]){
u = up[u][i], v = up[v][i];
}
return up[u][0];
}
int dis(int a, int b){
return depth[a] + depth[b] - 2 * depth[lca(a, b)];
}
namespace SUBTASK_4{
int dp[MAX], del[MAX];
bool vis[MAX];
int dfs(int u){
vis[u] = true;
int mx_node = u;
for (int&v : G[u]) if(!vis[v]){
if(del[v]) continue;
int x = dfs(v);
if(label[mx_node] < label[x]){
mx_node = x;
}
}
return mx_node;
}
void main(void){
queue<int> q;
q.emplace(root);
while(q.size()){
int u = q.front(); q.pop();
if(del[u]) continue;
del[u] = true;
for (int&v : G[u]){
memset(vis, 0, (numNode + 1) * sizeof(bool));
int x = dfs(v);
if(!del[x]){
if(maximize(dp[x], dp[u] + dis(x, u))){
q.push(x);
}
}
}
}
int ans = 0;
for (int i = 1; i <= numNode; ++i) maximize(ans, dp[i]);
cout << ans;
}
}
namespace SUBTASK_7{
int mx[MAX], pa[MAX];
int find(int u){
return u == pa[u] ? u : pa[u] = find(pa[u]);
}
bool joint(int u, int v){
u = find(u), v = find(v);
if(u == v) return false;
if(mx[u] < mx[v]){
swap(u, v);
}
pa[v] = u;
maximize(mx[u], mx[v]);
return true;
}
int dp[MAX];
int ID[MAX];
void main(void){
for (int i = 1; i <= numNode; ++i) mx[i] = label[i], pa[i] = i, ID[label[i]] = i;
memset(dp, 0, (numNode + 1) * sizeof(int));
int ans = 0;
for (int i = 1; i <= numNode; ++i){
int u = ID[i];
for (int&v : G[u]){
if (label[v] < label[u]){
int prv = find(v);
maximize(dp[u], dp[prv] + dis(prv, u));
joint(v, u);
}
}
maximize(ans, dp[u]);
}
cout << dp[ID[numNode]];
}
}
void process(void){
cin >> numNode;
for (int i = 1; i <= numNode; ++i){
cin >> label[i];
if(label[i] == numNode) root = i;
}
for (int i = 1; i < numNode; ++i){
int u, v; cin >> u >> v;
G[u].emplace_back(v);
G[v].emplace_back(u);
}
pre_dfs(root, root);
if(numNode <= 5000) {
SUBTASK_4 :: main();
return;
}
SUBTASK_7 :: main();
}
signed main(){
#define name "Whisper"
cin.tie(nullptr) -> sync_with_stdio(false);
//freopen(name".inp", "r", stdin);
//freopen(name".out", "w", stdout);
process();
return (0 ^ 0);
}
