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

int n,k;

typedef pair<int, int> P;


void solve()
{
	vector<bool> card(n+111);	// 111 is jork  @/w/@
	fill(card.begin(), card.end(), false);
	int ans = 0;

	int in;
	for(int i = 0; i < k; i++){
		cin >> in;
		card[in] = true;
	}

	int a = 0,b = 0;
	int i;
	for(i = 1; i <= n+1; i++){
		if(card[i]){
			a++;
		}
		else if(card[0]){
			a++;
			if(card[i+1]){
				int j = 1;
				while(card[i+j+1])j++;
				
				a += j;
				ans = max(ans, a);
				//cout << ans << endl;
				
			}
			else {
				ans = max(ans, a);
			}
			a = 0;

		}
		else {
			ans = max(ans, a);
			a = 0;
		}
	}

	cout << ans << endl;

}

int main(void)
{
	while(cin >> n >> k, n | k)
		solve();
	return 0;
}
### 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>
#include <vector>
using namespace std;

int n,k;

typedef pair<int, int> P;


void solve()
{
	vector<bool> card(n+111);	// 111 is jork  @/w/@
	fill(card.begin(), card.end(), false);
	int ans = 0;

	int in;
	for(int i = 0; i < k; i++){
		cin >> in;
		card[in] = true;
	}

	int a = 0,b = 0;
	int i;
	for(i = 1; i <= n+1; i++){
		if(card[i]){
			a++;
		}
		else if(card[0]){
			a++;
			if(card[i+1]){
				int j = 1;
				while(card[i+j+1])j++;
				
				a += j;
				ans = max(ans, a);
				//cout << ans << endl;
				
			}
			else {
				ans = max(ans, a);
			}
			a = 0;

		}
		else {
			ans = max(ans, a);
			a = 0;
		}
	}

	cout << ans << endl;

}

int main(void)
{
	while(cin >> n >> k, n | k)
		solve();
	return 0;
}
```