#include<iostream>
#include<algorithm>
using namespace std;

int dp[100000][2];
int main(){
	int n,k;
	while(cin>>n>>k,n||k){
		int ans=0;
		bool white=false;
		fill_n((int*)dp,n*2,0);
		for(int j=0;j<k;j++){
			int tmp;
			cin>>tmp;
			if(tmp)dp[tmp-1][0]=1;
			else white=true;
		}
		for(int i=1;i<n;i++){
			if(dp[i][0]==0)continue;
			if(dp[i-1][0]){
				dp[i][0] = dp[i-1][0]+1;
				dp[i][1] = dp[i-1][1]+1;
			}

			if(1<i && white && dp[i-2][0]){
				dp[i][1] = max(dp[i][1],dp[i-2][0]+2);
			}
			ans = max(ans,max(dp[i][0],dp[i][1]));
		}
		cout<<ans<<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<algorithm>
using namespace std;

int dp[100000][2];
int main(){
	int n,k;
	while(cin>>n>>k,n||k){
		int ans=0;
		bool white=false;
		fill_n((int*)dp,n*2,0);
		for(int j=0;j<k;j++){
			int tmp;
			cin>>tmp;
			if(tmp)dp[tmp-1][0]=1;
			else white=true;
		}
		for(int i=1;i<n;i++){
			if(dp[i][0]==0)continue;
			if(dp[i-1][0]){
				dp[i][0] = dp[i-1][0]+1;
				dp[i][1] = dp[i-1][1]+1;
			}

			if(1<i && white && dp[i-2][0]){
				dp[i][1] = max(dp[i][1],dp[i-2][0]+2);
			}
			ans = max(ans,max(dp[i][0],dp[i][1]));
		}
		cout<<ans<<endl;
	}
	return 0;
}
```