#include<iostream>
#include<memory.h>
#include<algorithm>
using namespace std;
int n, k;
int card[100001];
int ans = 0;
int main()
{
	cin >> n >> k;
	while (n!=0&&k!=0){
		memset(card, 0, sizeof(card));
		for (int i = 0; i < k; i++){
			int t;
			cin >> t;
			card[t] = 1;
		}
		int st = 1;
		int count = 0;
		for (int i = 1; i <= n + 1; i++){
			if (card[i] == 0){
				for (int i2 = st; i2 < i; i2++){
					card[i2] = count;
				}
				ans = max(ans, count);
				st = i + 1;
				count = 0;
			}
			else{
				count++;
			}
		}
		if (card[0] == 0){
			cout << ans << endl;
		}
		else{
			for (int i = 1; i <= n; i++){
				if (card[i] == 0){
					ans = max(ans, (card[i - 1] + card[i + 1]) + 1);
				}
			}
			cout << ans << endl;
		}
		cin >> n >> k;
	}
}
### 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<iostream>
#include<memory.h>
#include<algorithm>
using namespace std;
int n, k;
int card[100001];
int ans = 0;
int main()
{
	cin >> n >> k;
	while (n!=0&&k!=0){
		memset(card, 0, sizeof(card));
		for (int i = 0; i < k; i++){
			int t;
			cin >> t;
			card[t] = 1;
		}
		int st = 1;
		int count = 0;
		for (int i = 1; i <= n + 1; i++){
			if (card[i] == 0){
				for (int i2 = st; i2 < i; i2++){
					card[i2] = count;
				}
				ans = max(ans, count);
				st = i + 1;
				count = 0;
			}
			else{
				count++;
			}
		}
		if (card[0] == 0){
			cout << ans << endl;
		}
		else{
			for (int i = 1; i <= n; i++){
				if (card[i] == 0){
					ans = max(ans, (card[i - 1] + card[i + 1]) + 1);
				}
			}
			cout << ans << endl;
		}
		cin >> n >> k;
	}
}
```