#include<bits/stdc++.h>
using namespace std;
const int MAXN=2e5+5;
int n;
struct SegmentTree {
	#define mid ((l+r)>>1)
	struct Node {
		int ls,rs,max;
	}	tr[MAXN*150];
	int rt[MAXN<<2],tot;
	inline void ins(int ul,int ur,int k,int l,int r,int &p) {
		if(!p) p=++tot;
		if(ul<=l&&r<=ur) return tr[p].max=max(tr[p].max,k),void();
		if(ul<=mid) ins(ul,ur,k,l,mid,tr[p].ls);
		if(mid<ur) ins(ul,ur,k,mid+1,r,tr[p].rs);
	}
	inline int qry(int u,int l,int r,int p) {
		if(!p||l==r) return tr[p].max;
		return u<=mid?qry(u,l,mid,tr[p].ls):qry(u,mid+1,r,tr[p].rs);
	}
	inline void Ins(int ul,int ur,int vl,int vr,int k,int l=1,int r=n,int p=1) {
		if(ul<=l&&r<=ur) return ins(vl,vr,k,1,n,rt[p]);
		if(ul<=mid) Ins(ul,ur,vl,vr,k,l,mid,p<<1);
		if(mid<ur) Ins(ul,ur,vl,vr,k,mid+1,r,p<<1|1);
	}
	inline int Qry(int u,int v,int l=1,int r=n,int p=1) {
		if(l==r) return qry(v,1,n,rt[p]);
		return max(qry(v,1,n,rt[p]),u<=mid?Qry(u,v,l,mid,p<<1):Qry(u,v,mid+1,r,p<<1|1));
	}
	#undef mid
}	T;
vector <int> G[MAXN];
int c[MAXN],fa[MAXN],L[MAXN],R[MAXN],dfn[MAXN],dep[MAXN],up[MAXN][20],dcnt,dp[MAXN];
inline void dfs(int u) {
	L[u]=dfn[u]=++dcnt,dep[u]=dep[fa[u]]+1;
	for(int k=1;k<20;++k) up[u][k]=up[up[u][k-1]][k-1];
	for(int v:G[u]) if(v^fa[u]) fa[v]=up[v][0]=u,dfs(v);
	R[u]=dcnt;
}
inline int LCA(int u,int v) {
	if(dep[u]<dep[v]) swap(u,v);
	for(int k=19;~k;--k) if(dep[up[u][k]]>=dep[v]) u=up[u][k];
	if(u==v) return u;
	for(int k=19;~k;--k) if(up[u][k]^up[v][k]) u=up[u][k],v=up[v][k];
	return up[u][0];
}
inline int jump(int u,int rt) {
	for(int k=19;~k;--k) if(dep[up[u][k]]>dep[rt]) u=up[u][k];
	return u;
}
inline int dist(int u,int v) { return dep[u]+dep[v]-2*dep[LCA(u,v)]; }
int e[MAXN][2],ans=0;
struct Path { int u,v,w; };
vector <Path> P;
signed main() {
	scanf("%d",&n);
	for(int i=1;i<=n;++i) scanf("%d",&c[i]),e[c[i]][e[c[i]][0]>0]=i;
	for(int i=1,u,v;i<n;++i) scanf("%d%d",&u,&v),G[u].push_back(v),G[v].push_back(u);
	dfs(1);
	for(int i=1;i<=n;++i) if(e[i][1]) P.push_back({e[i][0],e[i][1],dist(e[i][0],e[i][1])});
	sort(P.begin(),P.end(),[&](auto u,auto v){ return u.w<v.w; });
	for(auto p:P) {
		int len=2+(p.w>1),u=p.u,v=p.v;
		if(dfn[u]>dfn[v]) swap(u,v);
		len=max(len,T.Qry(dfn[u],dfn[v])),ans=max(ans,len);
		if(p.w==dep[v]-dep[u]) {
			int z=jump(v,u);
			if(1<L[z]) T.Ins(1,L[z]-1,L[v],R[v],len);
			if(R[z]<n) T.Ins(L[v],R[v],R[z]+1,n,len);
		} else T.Ins(L[u],R[u],L[v],R[v],len);
	}
	printf("%d\n",ans);
	return 0;
}