RT。
所有样例都可以过。
所有Discuss里的东西也都OK。
然后WA了。

#include <cstdio>
#include <cstring>
#include <cctype>
#include <climits>
#include <algorithm>
using namespace std;

#define rep(i,a,b) for (int i=(a);i<=(b);i++)
#define per(i,a,b) for (int i=(a);i>=(b);i--)

const int N=32768;
const int MAX=INT_MAX>>1;

int n;
int s[N];
int t[N];

int ht[N],sa[N],rk[N];
int sum[N],tsa[N],trk[N];

int al,ar;
int mid;

inline int rd(void)
{
	int x=0,f=1; char c=getchar();
	for (;!isdigit(c);c=getchar()) if (c=='-') f=-1;
	for (;isdigit(c);c=getchar()) x=x*10+c-'0';
	return x*f;
}

int Check(int x)
{
	int minLoc,maxLoc; int cur;
	rep(i,2,n)
		if (ht[i]>=x)
		{
			minLoc=min(sa[i-1],sa[i]);
			maxLoc=max(sa[i-1],sa[i]);
			cur=i;
			while (cur+1<=n&&ht[cur+1]>=x)
			{
				cur++;
				minLoc=min(minLoc,sa[cur]);
				maxLoc=max(maxLoc,sa[cur]);
			}
			i=cur;
			if (minLoc+x<maxLoc) return 1;
		}
	return 0;
}

int main(void)
{
//	freopen("a.in","r",stdin);
//	freopen("a.out","w",stdout);
	
	rep(tur,1,MAX)
	{
		n=rd();
		if (!n) break;
		if (n==1)
		{
			printf("0\n");
			continue;
		}
		
		memset(s,0,sizeof s);
		rep(i,1,n)
			s[i]=rd();
		rep(i,1,n-1)
			s[i]=s[i+1]-s[i]+90;
		s[n--]=MAX;
		
		memset(ht,0,sizeof ht);
		memset(rk,0,sizeof rk);
		memset(sa,0,sizeof sa);
		memset(sum,0,sizeof sum);
		memset(tsa,0,sizeof tsa);
		memset(trk,0,sizeof trk);
		
		int lim=200,p;
		rep(i,1,n) sum[rk[i]=s[i]]++;
		rep(i,1,lim) sum[i]+=sum[i-1];
		per(i,n,1) sa[sum[rk[i]]--]=i;
		rk[sa[1]]=p=1;
		rep(i,2,n)
		{
			if (s[sa[i]]!=s[sa[i-1]]) p++;
			rk[sa[i]]=p;
		}
		lim=p;
		
		for (int j=1;lim!=n;j<<=1)
		{
			p=0; memset(tsa,0,sizeof tsa);
			rep(i,n-j+1,n) tsa[++p]=i;
			rep(i,1,n) if (sa[i]>j) tsa[++p]=sa[i]-j;
			
			memset(sum,0,sizeof sum);
			memmove(trk,rk,sizeof rk);
			rep(i,1,n) sum[rk[i]=trk[tsa[i]]]++;
			rep(i,1,lim) sum[i]+=sum[i-1];
			
			per(i,n,1) sa[sum[rk[i]]--]=tsa[i];
			rk[sa[1]]=p=1;
			rep(i,2,n)
			{
				if (trk[sa[i]]!=trk[sa[i-1]]||trk[sa[i]+j]!=trk[sa[i-1]+j]) p++;
				rk[sa[i]]=p;
			}
			lim=p;
		}
		
		p=0;
		rep(i,1,n)
		{
			if (p>0) p--;
			while (s[i+p]==s[sa[rk[i]-1]+p]) p++;
			ht[rk[i]]=p;
		}
		
		al=0,ar=n;
		while (al<=ar)
		{
			mid=(al+ar)>>1;
			if (Check(mid))
				al=mid+1;
			else ar=mid-1;
		}
		if (ar<4) printf("0\n");
		else printf("%d\n",ar+1);
	}
	
	return 0;
}