#include<iostream>
#include<cstdio>
#include<algorithm>
int main()
{
	int n,k;
	while(1){
		scanf("%d%d",&n,&k);	
		if(n==0&&k==0)
			break;
		
		const int K=100000;
		bool card[K+1]={false};
		for(int i=0;i!=k;++i){
			int c;
			scanf("%d",&c);
			card[c]=true;
		}	
	
		int before=-1;
		int m=0;
		if(card[0]){
			int no=-1;
			for(int i=1;i<=n;++i){
				if(card[i]){
					if(before==-1||!card[before])
						before=i;
				}
				else if(no==-1||before>no){
					no=i;
				}
				else if(before!=-1){
					m=std::max(m,i-before);
					before=no+1;
					no=i;
				}
			}
			if(before!=-1)
				m=std::max(m,n-before+1);
		}
		else{
			for(int i=1;i<=n;++i){
				if(card[i]){
					if(before==-1||!card[before])
						before=i;
				}
				else if(before!=-1){
					m=std::max(m,i-before);
					before=i+1;
				}
			}
			if(before!=-1)
				m=std::max(m,n-before+1);
		}
		std::cout<<m<<std::endl;
	}
	return 0;
}
### Prompt

In Cpp, your task is to solve 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<iostream>
#include<cstdio>
#include<algorithm>
int main()
{
	int n,k;
	while(1){
		scanf("%d%d",&n,&k);	
		if(n==0&&k==0)
			break;
		
		const int K=100000;
		bool card[K+1]={false};
		for(int i=0;i!=k;++i){
			int c;
			scanf("%d",&c);
			card[c]=true;
		}	
	
		int before=-1;
		int m=0;
		if(card[0]){
			int no=-1;
			for(int i=1;i<=n;++i){
				if(card[i]){
					if(before==-1||!card[before])
						before=i;
				}
				else if(no==-1||before>no){
					no=i;
				}
				else if(before!=-1){
					m=std::max(m,i-before);
					before=no+1;
					no=i;
				}
			}
			if(before!=-1)
				m=std::max(m,n-before+1);
		}
		else{
			for(int i=1;i<=n;++i){
				if(card[i]){
					if(before==-1||!card[before])
						before=i;
				}
				else if(before!=-1){
					m=std::max(m,i-before);
					before=i+1;
				}
			}
			if(before!=-1)
				m=std::max(m,n-before+1);
		}
		std::cout<<m<<std::endl;
	}
	return 0;
}
```