// credit: valeriu
#include <bits/stdc++.h>
using namespace std;
#define pii pair<long long, long long>
using ll = long long;
const int NMAX = 5e5;
const int VALMAX = 1e6;
const int LOGMAX = 18;
const int INF = 1e9;
const int MOD = 998244353;
mt19937 rnd( chrono::steady_clock::now().time_since_epoch().count() );
/*
#ifndef HOME
ifstream fin( "regate.in" );
ofstream fout( "regate.out" );
#define cin fin
#define cout fout
#endif // HOME
*/
vector <int> edges[NMAX+1];
pii h[NMAX+1];
int parent[NMAX+1];
int heavy[NMAX+1];
int find( int node ) {
if( parent[node] == node )
return node;
return parent[node] = find( parent[node] );
}
void unite( int a, int b ) {
a = find( a );
b = find( b );
if( a != b ) {
parent[b] = a;
heavy[a] = h[heavy[a]] > h[heavy[b]] ? heavy[a] : heavy[b];
}
}
int anc[NMAX+1][LOGMAX+1];
int dep[NMAX+1];
void dfs( int node, int par = 0 ) {
int i;
anc[node][0] = par;
dep[node] = dep[par] + 1;
for( i = 1; i < LOGMAX; i++ ) {
if( anc[node][i-1] != 0 )
anc[node][i] = anc[anc[node][i-1]][i-1];
}
for( auto vec: edges[node] ) {
if( vec != par )
dfs( vec, node );
}
}
int dist( int a, int b ) {
int ca = a, cb = b, i;
if( dep[a] < dep[b] )
swap( a, b );
int d = dep[a] - dep[b];
for( i = 0; i < LOGMAX; i++ ) {
if( d & ( 1 << i ) )
a = anc[a][i];
}
for( i = LOGMAX - 1; i >= 0; i-- ) {
if( anc[a][i] != anc[b][i] )
a = anc[a][i], b = anc[b][i];
}
if( a != b )
a = anc[a][0], b = anc[b][0];
return dep[ca] - dep[a] + dep[cb] - dep[a];
}
ll dp[NMAX+1], ord[NMAX+1];
void solve() {
int n, i, a, b, nxt;
cin >> n;
for( i = 1; i <= n; i++ ) {
cin >> h[i].first, h[i].second = i;
ord[i] = i;
}
for( i = 0; i < n - 1; i++ ) {
cin >> a >> b;
edges[a].push_back( b );
edges[b].push_back( a );
}
sort( ord + 1, ord + n + 1, []( int a, int b ) {
return h[a] < h[b];
} );
for( i = 1; i <= n; i++ )
parent[i] = i, heavy[i] = i;
dfs( 1 );
//cout << dist( 3, 5 ) << "\n";
for( i = 1; i <= n; i++ ) {
for( auto vec: edges[ord[i]] ) {
if( h[vec] < h[ord[i]] ) {
nxt = heavy[find(vec)];
dp[ord[i]] = max( dp[ord[i]], dp[nxt] + dist( nxt, ord[i] ) );
}
}
for( auto vec: edges[ord[i]] ) {
if( h[vec] < h[ord[i]] )
unite( vec, ord[i] );
}
}
cout << dp[ord[n]];
}
int main() {
ios_base::sync_with_stdio( false );
cin.tie( NULL );
cout.tie( NULL );
int t = 1;
//cin >> t;
while( t-- ) {
solve();
}
return 0;
}
