#include <bits/stdc++.h>
#define int long long
#define ll long long
#define pb push_back
#define fi first
#define se second
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
#define ld long double
using namespace std;
typedef pair<int,int> pii;
typedef pair<char,char> pcc;
typedef pair<int,pii> ipii;
typedef pair<pii,pii> ipiii;
const int MAXN = 2e5+30;
const int SQRT = 610;
const int MAXA = 5e5+10;
const int MOD = 1e6+7;
const int INF = 2e9+10;
const int LOG = 19;
const ld EPS = 1e-12;
void chmx(int &a, int b){ a = max(a,b); }
int n, h[MAXN];
vector <int> adj[MAXN];
int dep[MAXN], anc[MAXN][LOG+5];
void dfs(int nw, int par){
anc[nw][0] = par; dep[nw] = dep[par]+1;
for(auto nx : adj[nw]){
if(nx == par) continue;
dfs(nx, nw);
}
}
int LCA(int x, int y){
if(dep[x] > dep[y]) swap(x, y);
for(int i=LOG-1; i>=0; i--){
if(dep[anc[y][i]] >= dep[x])
y = anc[y][i];
}
if(x==y) return x;
for(int i=LOG-1; i>=0; i--){
if(anc[y][i] != anc[x][i])
y = anc[y][i], x = anc[x][i];
}
return anc[x][0];
}
struct dsu {
int par[MAXN];
void bd(){
for(int i=1; i<=n; i++) par[i] = i;
}
int f(int x){
return (par[x]==x ? x : par[x]=f(par[x]));
}
bool con(int x, int y){
return f(x) == f(y);
}
void mer(int x, int y){
x = f(x); y = f(y);
if(x==y) return;
par[x] = y;
}
} DSU;
bool tag[MAXN];
int dp[MAXN];
signed main(){
cin >> n;
vector <pii> vec;
for(int i=1; i<=n; i++){
cin >> h[i]; vec.pb({h[i],i});
}
sort(vec.begin(), vec.end());
for(int i=1; i<=n-1; i++){
int x, y; cin >> x >> y;
adj[x].pb(y); adj[y].pb(x);
}
DSU.bd();
dfs(1, 0);
for(int j=1; j<LOG; j++)
for(int i=1; i<=n; i++)
anc[i][j] = anc[anc[i][j-1]][j-1];
for(auto [x, nw] : vec){
for(auto nx : adj[nw]){
if(tag[nx]==0) continue;
int up = DSU.f(nx);
int lca = LCA(up, nw);
dp[nw] = max(dp[nw], dp[up] + dep[up]+dep[nw]-2*dep[lca]);
DSU.mer(up, nw);
}
tag[nw] = 1;
}
cout << dp[vec.back().se] << '\n';
}
