#include <bits/stdc++.h>
using namespace std;
int main(){
	int n,k;
	while(1){
		cin>>n>>k;
		if(n==0)	return 0;
		bool a[n+1];
		for(int i=0;i<=n;i++)	a[i]=false;
		int input;
		for(int i=0;i<k;i++){
			cin>>input;
			a[input]=true;
		}
		if(!a[0]){
			int ans=0,cnt=0;
			for(int i=1;i<=n;i++){
				if(a[i])	cnt++;
				else{
					ans=max(ans,cnt);
					cnt=0;
				}
			}
			cout<<max(ans,cnt)<<endl;
			continue;
		}
		int cnt=0;
		vector<int> data;
		for(int i=1;i<=n;i++){
			if(a[i])	cnt++;
			else{
				data.push_back(cnt);
				cnt=0;
			}
		}
		data.push_back(cnt);
		int ans=0;
		for(int i=1;i<(int)data.size();i++){
			ans=max(ans,data[i-1]+data[i]+1);
		}
		cout<<ans<<endl;
	}
}
### Prompt

Develop a solution in Cpp to the problem described below:

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 <bits/stdc++.h>
using namespace std;
int main(){
	int n,k;
	while(1){
		cin>>n>>k;
		if(n==0)	return 0;
		bool a[n+1];
		for(int i=0;i<=n;i++)	a[i]=false;
		int input;
		for(int i=0;i<k;i++){
			cin>>input;
			a[input]=true;
		}
		if(!a[0]){
			int ans=0,cnt=0;
			for(int i=1;i<=n;i++){
				if(a[i])	cnt++;
				else{
					ans=max(ans,cnt);
					cnt=0;
				}
			}
			cout<<max(ans,cnt)<<endl;
			continue;
		}
		int cnt=0;
		vector<int> data;
		for(int i=1;i<=n;i++){
			if(a[i])	cnt++;
			else{
				data.push_back(cnt);
				cnt=0;
			}
		}
		data.push_back(cnt);
		int ans=0;
		for(int i=1;i<(int)data.size();i++){
			ans=max(ans,data[i-1]+data[i]+1);
		}
		cout<<ans<<endl;
	}
}
```