#include<cstdio>
#include<vector>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<map>
#include<string>
const int N = 200300;
const int mod = 998244353;
using ll = long long;
const int INF = 0x3f3f3f3f;
int read(){
    int x=0,flag=1;char c;
    while((c=getchar())<'0' || c>'9') if(c=='-') flag=-1;
    while(c>='0' && c<='9') x=(x<<3)+(x<<1)+(c^48),c=getchar();
    return x*flag;
}
const int M = 2*N;
struct node{
    int to,next;
}q[M];
int head[N],ss,sz[N],mxs[N],Rt,curN, curRt[N],cursub[N],dfn[N],out[N],tm;bool vis[N];
int Rtst[N],Rted[N],FA[N];
void addedge(int x,int y)
{
    q[++ss]=(node){y,head[x]};head[x]=ss;
    q[++ss]=(node){x,head[y]};head[y]=ss;
}
void dfs1(int x,int fa)
{
    sz[x]=mxs[x]=1;
    for (int j=head[x];j;j=q[j].next)
    {
        int t=q[j].to;
        if (t==fa||vis[t]) continue;
        dfs1(t,x);
        sz[x]+=sz[t];
        mxs[x]=std::max(mxs[x], sz[t]);
    }
    mxs[x]=std::max(mxs[x], curN-sz[x]);
    if (mxs[x]<mxs[Rt]) Rt=x;   
}
void dfs2(int x,int fa)
{
    dfn[x]=++tm;
    curRt[x]=Rt;
    for (int j=head[x];j;j=q[j].next)
    {
        int t=q[j].to;
        if (t==fa||vis[t]) continue;
        FA[t]=x;
        dfs2(t,x);
    }
    out[x]=tm;
    //printf("dfn %d = [%d,%d]\n",x,dfn[x],out[x]);
}
void dfsSubRt(int x, int fa, int S, int T)
{
    if (x!=Rt) Rtst[x]=S,Rted[x]=T,cursub[x]=S;
    for (int j=head[x];j;j=q[j].next)
    {
        int t=q[j].to;
        if (t==fa||vis[t]) continue;
        dfsSubRt(t,x,x==Rt?dfn[t]:S, x==Rt?out[t]:T);
    }
}
const int SegN=N*80;
int SegRt[N],cc,ls[SegN],rs[SegN],tag[SegN],tre[SegN];
void col(int &i, int x, int F)
{
    if (!i) {
        i=++cc;
        tre[i]=tre[F];ls[i]=rs[i]=tag[i]=0;
    }
    tre[i]=std::max(tre[i],x);
    tag[i]=std::max(tag[i],x);
}
void pushdown(int i)
{
    if (tag[i])
    {
        col(ls[i], tag[i], i);
        col(rs[i], tag[i], i);
        tag[i]=0;
    }
}
void insert(int &i,int l,int r,int F,int L,int R,int x)
{
    i=++cc;
    tre[i]=tre[F];ls[i]=ls[F];rs[i]=rs[F];tag[i]=tag[F];
    if (L<=l&&r<=R) {col(i,x,i);return;}
    pushdown(i);
    int mid=(l+r)>>1;
    if (L<=mid) insert(ls[i],l,mid,ls[F],L,R,x);
    if (mid<R) insert(rs[i],mid+1,r,rs[F],L,R,x);
    tre[i]=std::max(tre[ls[i]],tre[rs[i]]);
}
int query(int i,int l,int r,int x)
{
    if (!i) return 0;
    if (l==r) return tre[i];
    pushdown(i);
    int mid=(l+r)>>1;
    if (x<=mid) return query(ls[i],l,mid,x);
    else return query(rs[i],mid+1,r,x);
}
int ans=1;int c[N],ton[N],cp[N];
void dfs3(int x,int fa)
{
    int u=cp[x];
    int L1=0,R1=0;
    int L2=0,R2=0;
    //printf("FA %d = %d\n",x,FA[x]);
    SegRt[x]=SegRt[fa];
    if (u && curRt[u]==Rt && (dfn[u]<dfn[x] || out[x]<out[u]))
    {
        int curlen = query(SegRt[fa],1,curN,dfn[u]) + 2;
        if (FA[x]!=u) curlen = std::max(curlen, 3);
        if (cursub[x]!=cursub[u]) ans=std::max(ans, curlen);
        //printf("query %d = %d\n",x,curlen);
        if (dfn[u]<=dfn[x] && out[u]>=out[x])
        {
            //if (u==Rt) 
            L1=1, R1=Rtst[x]-1, L2=Rted[x]+1, R2=out[Rt];
            //else L1=1, R1=dfn[u]-1, L2=out[u]+1, R2=out[Rt];
            //printf("x=%d u=%d add L1 = [%d,%d] L2=[%d,%d]\n",x,u,L1,R1,L2,R2);
            if (L1<=R1) insert(SegRt[x], 1, out[Rt], SegRt[x], L1, R1, curlen);
            if (L2<=R2) insert(SegRt[x], 1, out[Rt], SegRt[x], L2, R2, curlen);
        }else if (cursub[x]!=cursub[u])
        {
            L1=dfn[u];R1=out[u];
            insert(SegRt[x], 1, out[Rt], SegRt[x], L1, R1, curlen);
        }
    }
    for (int j=head[x];j;j=q[j].next)
    {
        int t=q[j].to;
        if (t==fa||vis[t]) continue;
        dfs3(t, x);
    }
}
void solve(int x)
{//printf("Rt=%d\n",x);
    vis[x]=true;
    FA[x]=0;
    cc=tm=0;
    cursub[x]=0;
    dfs2(x,0);
    dfsSubRt(x,0,0,0);
    SegRt[x]=0;
    dfs3(x, 0);
    for (int j=head[x];j;j=q[j].next)
    {
        int t=q[j].to;
        if (vis[t]) continue;
        Rt=0;curN=sz[t];
        dfs1(t, x);
        solve(Rt);
    }
}
int main()
{
    int n=read();
    curN=n;mxs[0]=INF;
    for (int i=1;i<=n;++i) c[i]=read();
    for (int i=1;i<=n;++i)
    {
        cp[i] = ton[c[i]];
        ton[c[i]]=i;
    }
    for (int i=1;i<=n;++i)
        if (!cp[i]&&ton[c[i]]!=i) cp[i]=ton[c[i]];
    for (int i=1;i<n;++i) addedge(read(),read());
    dfs1(1,0);
    solve(Rt);
    printf("%d",ans);
}