#include<bits/stdc++.h>
#define pb push_back
#define pli pair<int,int>
#define fi first
#define se second
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL);
using namespace std;
using ll=long long;
const ll maxN=2e5+10;
const ll inf=1e18;
const ll mod=1e9+7;
ll lab[maxN],h[maxN],P[maxN][18];
ll findset(ll x)
{
return lab[x]<0?x:lab[x]=findset(lab[x]);
}
void unite(ll u,ll v)
{
u=findset(u);
v=findset(v);
if(lab[u]>lab[v]) swap(u,v);
lab[u]+=lab[v];
lab[v]=u;
}
vector<ll>g[maxN];
void dfs(ll u,ll p)
{
P[u][0]=p;
for(int i=1;i<=17;i++) P[u][i]=P[P[u][i-1]][i-1];
for(int v:g[u])
{
if(v!=p)
{
h[v]=h[u]+1;
dfs(v,u);
}
}
}
ll lca(ll u,ll v)
{
if(h[u]<h[v]) swap(u,v);
for(int i=17;i>=0;i--) if(h[u]-(1<<i)>=h[v]) u=P[u][i];
if(u==v) return u;
for(int i=17;i>=0;i--) if(P[u][i]!=P[v][i]) u=P[u][i],v=P[v][i];
return P[u][0];
}
ll dis(ll u,ll v)
{
return h[u]+h[v]-2*h[lca(u,v)];
}
ll n,p[maxN],id[maxN],dp[maxN],mx[maxN];
void solve()
{
cin >> n ;
for(int i=1;i<=n;i++)
{
cin >> p[i];
id[p[i]]=i;lab[i]=-1;
}
for(int i=1;i<n;i++)
{
ll u,v;
cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
dfs(1,1);
for(int i=1;i<=n;i++)
{
ll u=id[i];
for(int v:g[u])
{
if(p[v]<p[u])
{
dp[u]=max(dp[u],dp[findset(v)]+dis(u,mx[findset(v)]));
unite(u,v);
}
}
dp[findset(u)]=dp[u];
mx[findset(u)]=u;
}
cout << dp[id[n]];
}
int main()
{
fastio
//freopen(TASKNAME".INP","r",stdin);
//freopen(TASKNAME".OUT","w",stdout);
solve();
}
