#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<string.h>

#define clear(x) memset(x,0,sizeof(x))

using namespace std;

const int MAXN=400000+100;

int count[MAXN];

void radix(int *str,int *a,int *b,int n,int m)

{

 clear (count);

 for(int i=0;i<n;++i)++count[str[a[i]]];

 for(int i=1;i<=m;++i)count[i]+=count[i-1];

 for(int i=n-1;i>=0;--i)b[--count[str[a[i]]]]=a[i];

}

 int rank[MAXN],a[MAXN],b[MAXN];

void sorted_suffix_array(int *str,int *sa,int n,int m)

{

 clear (rank);clear(a);clear(b);

 for(int i=0;i<n;++i)rank[i]=i;

 radix(str,rank,sa,n,m);

 rank[sa[0]]=0;

 for(int i=1;i<n;++i)rank[sa[i]]=rank[sa[i-1]]+(str[sa[i]]!=str[sa[i-1]]);

 for(int i=0;(1<<i) <n;++i)

 	{

 	 for(int j=0;j<n;++j)

 	 	{

 	 	 a[j]=rank[j]+1;

 	 	 b[j]=j+(1<<i)>=n? 0:rank[j+(1<<i)]+1;

 	 	 sa[j]=j;

		}

	 radix(b,sa,rank,n,n);

	 radix(a,rank,sa,n,n);

	 rank[sa[0]]=0;

	 for(int j=1;j<n;++j)

	 	{

	 	 rank[sa[j]]=rank[sa[j-1]]+(a[sa[j-1]]!=a[sa[j]]||b[sa[j-1]]!=b[sa[j]]);

		}

	}

}

int Rank[MAXN];

void calc_height(int *str,int *sa,int *h,int n)

{

 clear(Rank);

 int k=0;

 h[0]=0;

 for(int i=0;i<n;++i)Rank[sa[i]]=i;

 for(int i=0;i<n;++i)

 	{

 	 k= k==0?0:k-1;

 	 if(Rank[i]!=0)

 	   while(str[i+k]==str[sa[Rank[i]-1]+k])++k;

 	 h[Rank[i]]=k;

	}

}

 int s[MAXN],sa[MAXN],h[MAXN],duprank[MAXN];

string duplicate_substr(string str,bool is_joint)

{

 string rev;

 clear (s);clear(sa);clear(h);clear(duprank);

 int n=str.length();

 copy(str.begin(),str.end(),s);

 for(int i=0;i<n-1;i++)

    s[i]=s[i+1]-s[i]+100;

 n--;

 sorted_suffix_array(s,sa,n,500);

 calc_height(s,sa,h,n);

 int ans1=0,pos1=0;

 for(int i=0;i<n;i++)

 	duprank[sa[i]]=i;

 for(int i=0;i<n;i++)

 	{

     if(h[duprank[i]]>ans1){ans1=h[duprank[i]];pos1=i;}

	}

 if(is_joint)return str.substr(pos1,ans1);

 int low=0,high=n-1;

 int ans2=0,pos21=0,pos22=0;

 while(low<=high)

 	{

 	 int mid=(low+high)/2;

 	 bool ok=false;

 	 for(int i=0;i<n;)

 	 	{

 	 	 int j=i+1,minPos=sa[i],maxPos=sa[i];

		 while(j<n&&h[j]>=mid)

		 	{

		 	 minPos=min(minPos,sa[j]);

		 	 maxPos=max(maxPos,sa[j]);

		 	 j++;

			}

		 if((maxPos-minPos)>mid)

		 	{

		 	 ok=true;

		 	 if(mid>ans2)

		 	 	{

		 	 	 ans2=mid;

		 	 	 pos21=minPos;

		 	 	 pos22=maxPos;

				}

			 break;

			}

		 i=j;

		}

	 if(ok){low=mid+1;}

	 	else{high=mid-1;}

	}

 if(!is_joint)return str.substr(pos21,ans2);

}

int num[MAXN];

int main()

{freopen("t.txt","r",stdin);

 int n;

 while(scanf("%d",&n))

 	{

 	 string a;

 	 if(n==0)return 0;

 	 for(int i=0;i<n;i++)

 	 	{

 	 	 scanf("%d",&num[i]);

		}

	 for(int i=0;i<n;i++)

	 	{

	 	 char cc[2];

	 	 cc[0]=num[i];cc[1]=0;

	 	 a.append(cc);

		}

	 int ans=duplicate_substr(a,false).length()+1;

	 if(ans>=5)printf("%d\n",ans);

	 	else printf("0\n");

	}

 return 0;

}