#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 2e5 + 7;
const int M = 30;
int n,p[N],lift[N][M],depth[N];
vector < int > tree[N];
pair < int , int > ord[N];
inline void dfs(int node , int par , int dpt){
lift[node][0] = par;
depth[node] = dpt;
for(int i = 0;i<(int)tree[node].size();i++){
if(par != tree[node][i]){
dfs(tree[node][i],node,dpt+1);
}
}
}
inline int lca(int a , int b){
if(depth[a] > depth[b])swap(a,b);
int diff = depth[b] - depth[a];
for(int i = 0;i<M;i++){
if((diff >> i) & 1){
b = lift[b][i];
}
}
if(a == b)return a;
for(int i = M-1;i>=0;i--){
if(lift[a][i] != lift[b][i]){
a = lift[a][i];
b = lift[b][i];
}
}
return lift[a][0];
}
inline int dist(int a , int b){
return depth[a] + depth[b] - 2 * depth[lca(a,b)];
}
struct DSU{
vector < int > par,dp;
DSU(int x){
x += 3;
par.resize(x);
iota(par.begin() , par.end() , 0);
dp.assign(x,0);
}
int find(int a){
if(par[a] == a)return a;
return par[a] = find(par[a]);
}
void merge(int a , int b){//a -> b
a = find(a) , b = find(b);
dp[b] = max(dp[b] , dp[a] + dist(a,b) );
par[a] = b;
}
} dsu(N);
void solve(){
cin >> n;
for(int i = 0;i<n;i++){
cin >> p[i];
ord[i] = {p[i],i};
}
sort(ord , ord + n);
for(int i = 1;i<n;i++){
int ai,bi;cin >> ai >> bi;
ai--;bi--;
tree[ai].push_back(bi);
tree[bi].push_back(ai);
}
//calculating lca
dfs(0,0,0);
for(int i = 1;i<M;i++){
for(int j = 0;j<n;j++){
lift[j][i] = lift[lift[j][i-1]][i-1];
}
}
int ans = 0;
for(int i = 0;i<n;i++){
for(auto itr : tree[ord[i].second]){
if(p[itr] < ord[i].first){
dsu.merge(itr , ord[i].second);
}
}
ans = max(ans , dsu.dp[ord[i].second]);
}
cout << ans << endl;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int testcase = 1;//cin >> testcase;
while(testcase--)solve();
}
