/*
Things to notice:
1. do not calculate useless values
2. do not use similar names
 
Things to check:
1. submit the correct file
2. time (it is log^2 or log)
3. memory
4. prove your naive thoughts 
5. long long
6. corner case like n=0,1,inf or n=m
7. check if there is a mistake in the ds or other tools you use
8. fileio in some oi-contest

9. module on time 
10. the number of a same divisor in a math problem
11. multi-information and queries for dp and ds problems
*/
#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
const int mod=998244353;
const int inf=0x3f3f3f3f;
vector <int> g[200005];
struct LCA
{
	int dep[200005],dfn[200005],times;
	int st[20][400005],Lg[400005];
	void dfs(int u,int fa)
	{
		dfn[u]=++times,st[0][times]=u;
		for(int i=0;i<g[u].size();i++)
		{
			int v=g[u][i];
			if(v==fa) continue;
			dep[v]=dep[u]+1,dfs(v,u);
			st[0][++times]=u;
		}
	}
	int mindep(int x,int y)
	{
		if(dep[x]<dep[y]) return x;
		return y;
	}
	void build()
	{
		times=0,dep[1]=0;
		dfs(1,-1);
		Lg[1]=0,Lg[2]=1;
		for(int i=3;i<=times;i++) Lg[i]=Lg[i/2]+1;
		for(int k=1;k<20;k++) for(int i=1;i+(1<<k)-1<=times;i++) 
			st[k][i]=mindep(st[k-1][i],st[k-1][i+(1<<(k-1))]);
	}
	int getlca(int u,int v)
	{
		u=dfn[u],v=dfn[v];
		if(u>v) swap(u,v);
		int s=Lg[v-u+1];
		return mindep(st[s][u],st[s][v-(1<<s)+1]);
	}
	int getdist(int u,int v)
	{
		int lc=getlca(u,v);
		return dep[u]+dep[v]-2*dep[lc];
	}
}Lca;
int ls[40000005],rs[40000005],val[40000005],uidx;
void update(int id,int l,int r,int x,int d)
{
	val[id]=max(val[id],d);
	if(l==r) return;
	int mid=(l+r)>>1;
	if(x<=mid)
	{
		if(!ls[id]) ls[id]=++uidx;
		update(ls[id],l,mid,x,d);
	}
	else
	{
		if(!rs[id]) rs[id]=++uidx;
		update(rs[id],mid+1,r,x,d);
	}
}
int query(int id,int l,int r,int x,int y)
{
	if(!id) return 0;
	if(x<=l&&r<=y) return val[id];
	int mid=(l+r)>>1,res=0;
	if(x<=mid) res=max(res,query(ls[id],l,mid,x,y));
	if(y>mid) res=max(res,query(rs[id],mid+1,r,x,y));
	return res;
}
int Rt[400005],n;
void update2d(int id,int l,int r,int x1,int x2,int d)
{
	update(Rt[id],1,n,x2,d);
	if(l==r) return;
	int mid=(l+r)>>1;
	if(x1<=mid) update2d(id<<1,l,mid,x1,x2,d);
	else update2d(id<<1|1,mid+1,r,x1,x2,d);
} 
int query2d(int id,int l,int r,int x1,int y1,int x2,int y2)
{
	if(x1<=l&&r<=y1) return query(Rt[id],1,n,x2,y2);
	int mid=(l+r)>>1,res=0;
	if(x1<=mid) res=max(res,query2d(id<<1,l,mid,x1,y1,x2,y2));
	else res=max(res,query2d(id<<1|1,mid+1,r,x1,y1,x2,y2));
	return res;
}
vector <int> has[200005];
int c[200005];
int dfn[200005],R[200005],clk;
void dfs0(int u,int fa)
{
	dfn[u]=R[u]=++clk;
	for(int i=0;i<g[u].size();i++)
	{
		int v=g[u][i];
		if(v==fa) continue;
		dfs0(v,u),R[u]=R[v];
	}
}
void solve()
{
	cin>>n;
	for(int i=1;i<=n;i++) cin>>c[i],has[c[i]].pb(i);
	for(int i=1;i<=4*n;i++) Rt[i]=++uidx;
	for(int i=1;i<n;i++)
	{
		int u,v;
		cin>>u>>v;
		g[u].pb(v),g[v].pb(u);
	}
	Lca.build();
	vector <pii > vec;
	for(int i=1;i<=n;i++) if(has[i].size()==2) vec.pb(mp(Lca.getdist(has[i][0],has[i][1]),i));
	sort(vec.begin(),vec.end()),reverse(vec.begin(),vec.end());
	int ans=1;
	dfs0(1,-1);
	for(int i=0;i<vec.size();i++)
	{
		int col=vec[i].se;
		int u=has[col][0],v=has[col][1];
//		cout<<u<<" "<<v<<"\n";
		int dp=2;
		if(dfn[u]>dfn[v]) swap(u,v);
		if(dfn[u]<=dfn[v]&&dfn[v]<=R[u])
		{
//			cout<<"1.\n"; 
			int u2=u;
			for(int j=0;j<g[u].size();j++) if(Lca.getlca(v,g[u][j])==g[u][j]) u2=g[u][j];
			if(dfn[u2]-1) dp=max(dp,query2d(1,1,n,dfn[v],R[v],1,dfn[u2]-1)+2),dp=max(dp,query2d(1,1,n,1,dfn[u2]-1,dfn[v],R[v])+2);
			if(R[u2]+1<=n)  dp=max(dp,query2d(1,1,n,dfn[v],R[v],R[u2]+1,n)+2),dp=max(dp,query2d(1,1,n,R[u2]+1,n,dfn[v],R[v])+2);
//			cout<<"...\n";
		} 
		else
		{
//			cout<<"2.\n";
			dp=max(dp,query2d(1,1,n,dfn[u],R[u],dfn[v],R[v])+2);
			dp=max(dp,query2d(1,1,n,dfn[v],R[v],dfn[u],R[u])+2);
//			cout<<"...\n";
		}
		
		update2d(1,1,n,dfn[u],dfn[v],dp);
//		update2d(1,1,n,dfn[v],dfn[u],dp);
		if(Lca.getdist(u,v)!=1) dp++;
		ans=max(ans,dp);
//		cout<<"...\n";
	}
	cout<<ans<<"\n";
}
signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	int _=1;
//	cin>>_;
	while(_--) solve();
	return 0;
}