#include <cstdio>
#include <algorithm>
using namespace std;
int n,k;
bool used[100001]={};
int num[100001];
int main(){
while(1){
		fill(used,used+100001,false);
	scanf("%d %d",&n,&k);
if(!n) break;
	for(int i=0;i<k;i++){
		scanf("%d",&num[i]);
		used[num[i]]=true;
	}
	sort(num,num+k);
	int s=0,e=0,sum=0,res=0;
	if(used[0]){
		for(;;){
			while(e<=n && sum<=1){
				if(!used[e]){
					sum++;
					e++;
				}else{
					e++;
				}
			}
			if(sum<=1){
                                res=max(res,e-s);
				break;
			}
			res=max(res,e-s);
			if(!used[s]){
				sum--;
			}
			s++;
		}
	}else{
                e=1;s=1;
		for(;;){
			while(e<=n && sum<=0){
				if(!used[e]){
					sum++;
					e++;
				}else{
					e++;
				}
			}
			if(sum<=0){
				break;
			}
			res=max(res,e-s);
			if(!used[s]){
				sum--;
			}
			s++;
		}
	}
	printf("%d\n",res-1);
}
}
### Prompt

Please create a solution in cpp to the following problem:

problem

There are n cards with one integer from 1 to n and one blank card. Of these n + 1 cards, k cards are given, but 1 ≤ k ≤ n. You can write one integer from 1 to n on a blank card. I want to make a continuous sequence of integers as long as possible with just a given card.

Write a program that outputs the maximum length of a contiguous sequence of integers that can be made from a given card when the given card is entered.



input

The input consists of multiple datasets. Each dataset is given in the following format. The input ends on a line containing two zeros.

On the first line, two integers n (1 ≤ n ≤ 100000) and k (1 ≤ k ≤ n) are written in this order, separated by one blank. The following k line contains one integer. Written one by one, representing the integers written on the given k cards. Blank cards are represented by 0.

Of the scoring data, 40% of the points are 1 ≤ n ≤ 1000, 1 ≤ k ≤ 500, 20% of the points are 1 ≤ n ≤ 60000, 1 ≤ k ≤ 50000. Satisfy 1 ≤ n ≤ 100000, 1 ≤ k ≤ 100000.

The number of datasets does not exceed 5.

output

Outputs an integer on one line for each dataset.

Examples

Input

7 5
6
2
4
7
1
7 5
6
2
0
4
7
0 0


Output

2
4


Input

None


Output

None

### Response

```cpp
#include <cstdio>
#include <algorithm>
using namespace std;
int n,k;
bool used[100001]={};
int num[100001];
int main(){
while(1){
		fill(used,used+100001,false);
	scanf("%d %d",&n,&k);
if(!n) break;
	for(int i=0;i<k;i++){
		scanf("%d",&num[i]);
		used[num[i]]=true;
	}
	sort(num,num+k);
	int s=0,e=0,sum=0,res=0;
	if(used[0]){
		for(;;){
			while(e<=n && sum<=1){
				if(!used[e]){
					sum++;
					e++;
				}else{
					e++;
				}
			}
			if(sum<=1){
                                res=max(res,e-s);
				break;
			}
			res=max(res,e-s);
			if(!used[s]){
				sum--;
			}
			s++;
		}
	}else{
                e=1;s=1;
		for(;;){
			while(e<=n && sum<=0){
				if(!used[e]){
					sum++;
					e++;
				}else{
					e++;
				}
			}
			if(sum<=0){
				break;
			}
			res=max(res,e-s);
			if(!used[s]){
				sum--;
			}
			s++;
		}
	}
	printf("%d\n",res-1);
}
}
```