#include <iostream>
#include <chrono>
#include <vector>
#define maxn 200005
#define maxlog 20
#define INF 1000000010
#define LINF 1000000000000000005
#define endl '\n'
#define pb(x) push_back(x)
#define X first
#define Y second
#define control cout<<"passed"<<endl;
#pragma GCC optimize("O3" , "Ofast" , "unroll-loops" , "fast-math")
#pragma GCC target("avx2")
using namespace std;
std::chrono::high_resolution_clock::time_point startT, currT;
constexpr double TIME_MULT = 1;
double timePassed()
{
using namespace std::chrono;
currT = high_resolution_clock::now();
double time = duration_cast<duration<double>>(currT - startT).count();
return time * TIME_MULT;
}
int n;
int h[maxn] , depth[maxn];
vector <int> v[maxn];
void read()
{
cin >> n;
for(int i = 1; i <= n; i++)
cin >> h[i];
int from , to;
for(int i = 1; i < n; i++)
{
cin >> from >> to;
v[h[from]].pb(h[to]);
v[h[to]].pb(h[from]);
}
}
int bin_lift[maxn][maxlog];
void dfs(int node , int _parent)
{
for(int nb : v[node])
{
if(nb == _parent)
continue;
depth[nb] = depth[node] + 1;
bin_lift[nb][0] = node;
dfs(nb , node);
}
}
void calc()
{
for(int i = 1; i < maxlog; i++)
for(int j = 1; j <= n; j++)
bin_lift[j][i] = bin_lift[bin_lift[j][i - 1]][i - 1];
}
int get_distance(int a , int b)
{
int dist = 0;
if(depth[b] > depth[a])
swap(a ,b);
int need = depth[a] - depth[b];
for(int power = maxlog - 1; power > -1; power--)
{
if(need >= (1 << power))
{
a = bin_lift[a][power];
dist += (1 << power);
need -= (1 << power);
}
}
if(a == b)
return dist;
for(int power = maxlog - 1; power > -1; power--)
{
if(bin_lift[a][power] != bin_lift[b][power])
{
a = bin_lift[a][power];
b = bin_lift[b][power];
dist += (1 << (power + 1));
}
}
return (dist + 2);
}
int parent[maxn];
int find_parent(int node)
{
///cout << node << endl;
return parent[node] == -1? node : parent[node] = find_parent(parent[node]);
}
int pom[maxn];
void solve()
{
for(int i = 1; i <= n; i++)
parent[i] = -1;
for(int node = 1; node <= n; node++)
for(int nb : v[node])
{
nb = find_parent(nb);
///control
if(nb <= node)
{
int d = get_distance(node , nb);
pom[node] = max(pom[node] , pom[nb] + d);
parent[nb] = node;
}
}
cout << pom[n] << endl;
}
int main()
{
/**#ifdef ONLINE_JUDGE
freopen("taxi.in", "r", stdin);
freopen("taxi.out", "w", stdout);
#endif*/
/**ios_base::sync_with_stdio(false);
cin.tie(nullptr);*/
startT = std::chrono::high_resolution_clock::now();
read();
///control
dfs(1 , -1);
///control
calc();
///control
solve();
return 0;
}
