#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
#define p(x,y) pair<ll,ll>(x,y)
#define BIT(i,x) ((x>>i)&1)
#define MASK(x) (1<<x)
#define ld long double
#define __builtin_popcount __builtin_popcountll
#define pll pair<ll,ll>
template<class T1,class T2>
bool maximize(T1 &x,const T2 &y)
{
if(x<y)
{
x=y;
return 1;
}
return 0;
}
template<class T1,class T2>
bool minimize(T1 &x,const T2 &y)
{
if(x>y)
{
x=y;
return 1;
}
return 0;
}
void online()
{
std::ios_base::sync_with_stdio(0);
cin.tie(0);
}
const ll N=2e5+10;
ll par[N][30],lv[N],dis[N],a[N],r[N],n;
vector<ll> gr[N];
void dfs(ll u)
{
for(auto v:gr[u])
{
if(v==par[u][0]) continue;
par[v][0]=u;
lv[v]=lv[u]+1;
dis[v]=dis[u]+1;
dfs(v);
}
}
ll dist(ll u,ll v)
{
ll res=dis[u]+dis[v];
if(lv[u]<lv[v]) swap(u,v);
for(int i=20;i>=0;i--) if(lv[par[u][i]]>=lv[v]) u=par[u][i];
if(u==v) return res-2*dis[u];
for(int i=20;i>=0;i--)
{
if(par[u][i]!=par[v][i]) u=par[u][i],v=par[v][i];
}
u=par[u][0];
return res-2*dis[u];
}
struct DSU
{
ll n;
vector<ll> best,f,lab;
DSU(ll _n=0)
{
n=_n;
f.resize(n+2);
lab.resize(n+2,-1);
best.resize(n+2);
}
ll root(ll x)
{
return lab[x]<0?x:lab[x]=root(lab[x]);
}
ll join(ll x,ll y)
{
if(best[x]==0||best[y]==0) return 0;
if((x=root(x))==(y=root(y))) return 0;
if(lab[x]>lab[y]) swap(x,y);
lab[x]+=lab[y];
lab[y]=x;
return 1;
}
};
int main()
{
online();
cin>>n;
for(int i=1;i<=n;i++)
{
cin>>a[i];
r[a[i]]=i;
}
for(int i=1;i<n;i++)
{
ll u,v;
cin>>u>>v;
gr[u].push_back(v);
gr[v].push_back(u);
}
dfs(1);
for(int i=1;i<=20;i++)
{
for(int j=1;j<=n;j++) par[j][i]=par[par[j][i-1]][i-1];
}
DSU S(n);
for(int i=1;i<=n;i++)
{
ll u=r[i];
S.best[u]=i;
ll c=0;
for(auto V:gr[u])
{
ll v=S.root(V);
if(S.best[v]==0) continue;
maximize(c,S.f[v]+dist(u,r[S.best[v]]));
}
for(auto v:gr[u]) S.join(u,v);
S.best[S.root(u)]=i;
S.f[S.root(u)]=c;
}
ll ans=0;
for(int i=1;i<=n;i++)
{
maximize(ans,S.f[i]);
}
cout<<ans;
}
