#include <bits/stdc++.h>
typedef long long ll;
#define FOR(i,x,y) for(ll i=x; i<y; i++)
#define FORNEG(i,x,y) for(ll i=x; i>y; i--)
using namespace std;
const ll maxn = 200005;
ll vals[maxn];
ll which[maxn+2];
bool visited[maxn];
vector<ll> edges[maxn];
vector<vector<ll>> edges2[maxn];
ll cmp[maxn];
ll maxis[maxn];
ll ancc[maxn][30];
ll depth[maxn];
ll par[maxn];
ll anc(ll a, ll x){
if (a==0) return 0;
if (x==0) return par[a];
if (ancc[a][x] != -1) return ancc[a][x];
return ancc[a][x] = anc(anc(a,x-1),x-1);
}
ll lca(ll a, ll b){
if (depth[a] < depth[b]) swap(a,b);
FORNEG(i,29,-1) if (depth[anc(a,i)] >= depth[b]) a = anc(a,i);
if (a==b) return a;
FORNEG(i,29,-1) if (anc(a,i) != anc(b,i)) a = anc(a,i), b = anc(b,i);
return par[a];
}
void initdfs(ll a, ll p, ll d){
depth[a] = d;
par[a] = p;
for (auto&i : edges[a]) if (i != p) initdfs(i, a, d+1);
}
ll find(ll a){
while (a != cmp[a]){
cmp[a] = cmp[cmp[a]];
a = cmp[a];
}
return a;
}
void unite(ll a, ll b){
ll A = find(a);
ll B = find(b);
maxis[B] = max(maxis[B], maxis[A]);
cmp[A] = B;
}
ll dp(ll a, ll p){
ll ans = 0;
for (auto&i : edges2[a]){
if (i[0] != p) ans = max(ans, dp(i[0], a) + i[1]);
}
return ans;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll n;
cin >> n;
FOR(i,0,maxn) cmp[i] = i, maxis[i] = -1;
FOR(i,0,maxn) FOR(j,0,30) ancc[i][j] = -1;
FOR(i,0,n){
cin >> vals[i];
which[vals[i]] = i;
maxis[find(i)] = vals[i];
}
FOR(i,0,n-1){
ll a,b;
cin >> a >> b;
a--;b--;
edges[a].push_back(b);
edges[b].push_back(a);
}
initdfs(0,-1,0);
FOR(i,1,n+1){
ll root = which[i];
for (auto&i : edges[root]){
if (vals[i] > vals[root]) continue;
ll maxi = which[maxis[find(i)]];
edges2[root].push_back({maxi, depth[root]+depth[maxi] - 2*depth[lca(root, maxi)]});
unite(root, i);
}
}
ll root = which[n];
cout << dp(root, -1);
}
