#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main(){
	while(1){
		int ans=0,p=0,n,k,x,a[100001]={},flag=0,sflag=0;
		vector<int> V;
		cin>>n>>k;
		if(n==0 && k==0)
			break;
		for(int i=0;i<k;i++){
			cin>>x;
			if(x==0)
			flag=1;
			a[x]=1;
		}
		for(int i=1;i<=n;i++){
			if(sflag==0 && a[i])
				sflag=1;
			if(sflag){
				if(a[i])
					p++;
				else{
					sflag=0;
					V.push_back(p);
					p=0;
				}
			}
		}
		V.push_back(p);
		if(flag){
			for(int i=0;i<V.size()-1;i++)
				ans=max(V[i]+V[i+1]+1,ans);
		}else{
			for(int i=0;i<V.size();i++)
				ans=max(V[i],ans);
		}
		cout<<ans<<endl;
	}
	return 0;
}
### Prompt

Your challenge is to write a Cpp solution 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<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main(){
	while(1){
		int ans=0,p=0,n,k,x,a[100001]={},flag=0,sflag=0;
		vector<int> V;
		cin>>n>>k;
		if(n==0 && k==0)
			break;
		for(int i=0;i<k;i++){
			cin>>x;
			if(x==0)
			flag=1;
			a[x]=1;
		}
		for(int i=1;i<=n;i++){
			if(sflag==0 && a[i])
				sflag=1;
			if(sflag){
				if(a[i])
					p++;
				else{
					sflag=0;
					V.push_back(p);
					p=0;
				}
			}
		}
		V.push_back(p);
		if(flag){
			for(int i=0;i<V.size()-1;i++)
				ans=max(V[i]+V[i+1]+1,ans);
		}else{
			for(int i=0;i<V.size();i++)
				ans=max(V[i],ans);
		}
		cout<<ans<<endl;
	}
	return 0;
}
```