#include <bits/stdc++.h>
#define pb push_back
#define fst first
#define snd second
#define fore(i,a,b) for(ll i=a,ggdem=b;i<ggdem;++i)
#define SZ(x) ((int)x.size())
#define ALL(x) x.begin(),x.end()
#define mset(a,v) memset((a),(v),sizeof(a))
#define FIN ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define imp(v) for(auto messi:v)cout<<messi<<" "; cout<<"\n"
using namespace std;
typedef long long ll;
typedef pair<ll,ll> ii;
const ll MAXN=2e5+5;
ll uf[MAXN],pa[MAXN];
ll uf_find(ll x){return uf[x]<0?x:uf[x]=uf_find(uf[x]);}
void uf_join(ll x, ll y){
x=uf_find(x),y=uf_find(y);
if(-uf[x]>-uf[y])swap(x,y);
uf[x]+=uf[y];
uf[y]=x;
}
ll dp[MAXN];
vector<ll>g[MAXN]; ll n;
const ll K=18; //K such that 2^K>=n
ll F[K][MAXN],D[MAXN];
void lca_dfs(ll x){
for(auto y:g[x]){
if(y==F[0][x])continue;
F[0][y]=x;D[y]=D[x]+1;lca_dfs(y);
}
}
void lca_init(){
D[0]=0;F[0][0]=-1;
lca_dfs(0);
fore(k,1,K)fore(x,0,n){
if(F[k-1][x]<0)F[k][x]=-1;
else F[k][x]=F[k-1][F[k-1][x]];
}
}
ll lca(ll x,ll y){
if(D[x]<D[y])swap(x,y);
for(ll k=K-1;k>=0;k--)if(D[x]-(1ll<<k)>=D[y])x=F[k][x];
if(x==y)return x;
for(ll k=K-1;k>=0;k--)if(F[k][x]!=F[k][y])x=F[k][x],y=F[k][y];
return F[0][x];
}
ll dis(ll x, ll y){return D[x]+D[y]-2*D[lca(x,y)];}
int main(){FIN;
cin>>n;
vector<ll>a(n),p(n);
fore(i,0,n)cin>>a[i],a[i]--,p[a[i]]=i;
fore(i,0,n-1){
ll u,v; cin>>u>>v; u--,v--;
g[u].pb(v);
g[v].pb(u);
}
mset(uf,-1);
lca_init();
fore(i,0,n){
auto x=p[i];
for(auto y:g[x])if(a[y]<a[x]){
y=pa[uf_find(y)];
dp[x]=max(dp[x],dp[y]+dis(x,y));
uf_join(x,y);
}
pa[uf_find(x)]=x;
}
cout<<dp[p[n-1]]<<"\n";
return 0;
}
