// 2011/09/28 Tazoe

#include <iostream>
using namespace std;

int main()
{
	while(true){
		int n, k;
		cin >> n >> k;
		if(n==0&&k==0)
			break;

		int C[100003] = {0};
		for(int i=0; i<k; i++){
			int c;
			cin >> c;
			C[c] = 1;
		}

		int max = 1;

		if(C[0]==0){
			int sum = 0;
			for(int i=1; i<=n+1; i++)
				if(C[i]==1)
					sum++;
				else{
					if(max<sum)
						max = sum;
					sum = 0;
				}
			cout << max << endl;
			continue;
		}

		if(C[0]==1){
			int sum = 0;
			int sum2 = 0;
			for(int i=1; i<=n+2; i++)
				if(C[i]==1){
					sum++;
					sum2++;
				}
				else{
					if(max<sum2)
						max = sum2;
					sum2 = sum;
					sum2++;
					sum = 0;
				}
			cout << max << endl;
			continue;
		}
	}

	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
// 2011/09/28 Tazoe

#include <iostream>
using namespace std;

int main()
{
	while(true){
		int n, k;
		cin >> n >> k;
		if(n==0&&k==0)
			break;

		int C[100003] = {0};
		for(int i=0; i<k; i++){
			int c;
			cin >> c;
			C[c] = 1;
		}

		int max = 1;

		if(C[0]==0){
			int sum = 0;
			for(int i=1; i<=n+1; i++)
				if(C[i]==1)
					sum++;
				else{
					if(max<sum)
						max = sum;
					sum = 0;
				}
			cout << max << endl;
			continue;
		}

		if(C[0]==1){
			int sum = 0;
			int sum2 = 0;
			for(int i=1; i<=n+2; i++)
				if(C[i]==1){
					sum++;
					sum2++;
				}
				else{
					if(max<sum2)
						max = sum2;
					sum2 = sum;
					sum2++;
					sum = 0;
				}
			cout << max << endl;
			continue;
		}
	}

	return 0;
}
```