题目
还是板子题
因为旋律会同时加减一个数，所以我们在差分数组上做就好了
注意因为差分了，跨越的个数要少一个
基数排序循环写反了，调了好久
qwq

/*
@Date    : 2019-07-19 10:17:22
@Author  : Adscn (adscn@qq.com)
@Link    : https://www.cnblogs.com/LLCSBlog
*/
#include<bits/stdc++.h>
using namespace std;
#define IL inline
#define RG register
#define gi getint()
#define gc getchar()
#define File(a) freopen(a".in","r",stdin);freopen(a".out","w",stdout)
IL int getint()
{RG int xi=0;RG char ch=gc;bool f=0;while(ch<'0'|ch>'9')ch=='-'?f=1:f,ch=gc;while(ch>='0'&ch<='9')xi=(xi<<1)+(xi<<3)+ch-48,ch=gc;return f?-xi:xi;
}
template<typename T>
IL void pi(T k,char ch=0)
{if(k<0)k=-k,putchar('-');if(k>=10)pi(k/10,0);putchar(k%10+'0');if(ch)putchar(ch);
}
const int N=2e5+7;
int n;
int a[N];
namespace SA{int rkx[N],rky[N],rank[N],sa[N],*key1=rkx,*key2=rky;int height[N];int cnt[N],m=380;inline void init(){m=380;}inline void Qsort(){memset(cnt,0,sizeof cnt);for(int i=1;i<=n;++i)++cnt[key1[i]];for(int i=1;i<=m;++i)cnt[i]+=cnt[i-1];for(int i=n;i>=1;--i)sa[cnt[key1[key2[i]]]--]=key2[i];}inline void getsa(){key1=rkx,key2=rky;for(int i=1;i<=n;++i)key1[i]=a[i],key2[i]=i;Qsort();for(int k=1,p=0;p<n;k<<=1,m=p){p=0;for(int i=n-k+1;i<=n;++i)key2[++p]=i;for(int i=1;i<=n;++i)if(sa[i]>k)key2[++p]=sa[i]-k;Qsort();swap(key1,key2);p=key1[sa[1]]=1;for(int i=2;i<=n;++i)key1[sa[i]]=(key2[sa[i-1]]==key2[sa[i]]&&key2[sa[i-1]+k]==key2[sa[i]+k])?p:++p;}for(int i=1;i<=n;++i)rank[sa[i]]=i;}inline void getheight(){for(int i=1,k=0;i<=n;++i){if(k)--k;int s=sa[rank[i]-1];while(a[s+k]==a[i+k])++k;height[rank[i]]=k;}}
}
using namespace SA;
int check(int mid)
{int mx=sa[1],mn=sa[1];for(int i=2;i<=n;++i)if(height[i]<mid)mx=mn=sa[i];else{mn=min(sa[i],mn),mx=max(sa[i],mx);if(mx-mn>mid)return 1;}return 0;
}
int main(void)
{while(~scanf("%d",&n)){if(n==0)break;for(int i=1;i<=n;++i)a[i]=gi;--n;for(int i=1;i<=n;++i)a[i]=a[i+1]-a[i]+90;init();getsa();getheight();int l=0,r=n,ans;while(l<=r){int mid=(l+r)>>1;if(check(mid))ans=mid,l=mid+1;else r=mid-1;}printf("%d\n",ans<4?0:ans+1);return 0;}return 0;
}