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

int main(){
	int n, k;
	
	while( cin >> n >> k , n || k ){
		int C[100002] = {0};
		int dp[100002] = {0};
		
		for(int i=0 ; i < k ; i++ ){
			int j;
			cin >> j;
			C[j] = 1;
		}
		if( C[1] == 1 ){
			dp[1] = 1;
		}
		for(int i=2 ; i <= n ; i++ ){
			if( C[i] == 1 ){
				if( dp[i-1] > 0 ){
					dp[i] = dp[i-1] + 1;
				}else{
					dp[i] = 1;
				}
			}
		}
		for(int i=n ; i > 0 ; i-- ){
			if( C[i] == 1 ){
				if( dp[i+1] > 0 ){
					dp[i] = dp[i+1];
				}
			}
		}
		int ans = 0;
		if( C[0] == 1 ){
			for(int i=2 ; i <= n ; i++ ){
				ans = max( ans , dp[i] );
				if( C[i] == 0 ){
					ans = max( ans , dp[i-1] + dp[i+1] + 1 );
				}
			}
		}else{
			for(int i=1 ; i <= n ; i++ ){
				ans = max( ans , dp[i] );
			}
		}
		cout << ans << endl;
	}
}
### Prompt

Construct a cpp code solution to the problem outlined:

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 main(){
	int n, k;
	
	while( cin >> n >> k , n || k ){
		int C[100002] = {0};
		int dp[100002] = {0};
		
		for(int i=0 ; i < k ; i++ ){
			int j;
			cin >> j;
			C[j] = 1;
		}
		if( C[1] == 1 ){
			dp[1] = 1;
		}
		for(int i=2 ; i <= n ; i++ ){
			if( C[i] == 1 ){
				if( dp[i-1] > 0 ){
					dp[i] = dp[i-1] + 1;
				}else{
					dp[i] = 1;
				}
			}
		}
		for(int i=n ; i > 0 ; i-- ){
			if( C[i] == 1 ){
				if( dp[i+1] > 0 ){
					dp[i] = dp[i+1];
				}
			}
		}
		int ans = 0;
		if( C[0] == 1 ){
			for(int i=2 ; i <= n ; i++ ){
				ans = max( ans , dp[i] );
				if( C[i] == 0 ){
					ans = max( ans , dp[i-1] + dp[i+1] + 1 );
				}
			}
		}else{
			for(int i=1 ; i <= n ; i++ ){
				ans = max( ans , dp[i] );
			}
		}
		cout << ans << endl;
	}
}
```