#include <algorithm>
#include <cstdio>
int dp[100000], dp2[100000], v[100000];
int main()
{
	int n, k;
	while (scanf("%d%d", &n, &k), n|k) {
		int w = 0;
		for (int i=0; i<k; ++i) {
			int t;
			scanf("%d", &t);
			if (t == 0)
				w = 1;
			else
				v[i-w] = t;
		}
		std::sort(v, v+k-w);
		dp[0] = 1;
		for (int i=1; i<k-w; ++i)
			dp[i] = v[i]-v[i-1]==1 ? dp[i-1]+1 : 1;
		bool used = false;
		if (w) {
			dp2[0] = 1, dp2[k-w] = 1000011;
			for (int i=1; i<k-w; ++i) {
				if (v[i] - v[i-1] == 1) {
					dp2[i] = dp2[i-1]+1;
				}
				else {
					if (v[i] - v[i-1] == 2) {
						dp2[i] = dp[i-1] + 2;
						used = true;
					}
					else {
						dp2[i] = 1;
					}
				}
			}
		}
		printf("%d\n", std::max(*std::max_element(dp, dp+k-w), *std::max_element(dp2, dp2+k-w)+!used));
	}
	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 <algorithm>
#include <cstdio>
int dp[100000], dp2[100000], v[100000];
int main()
{
	int n, k;
	while (scanf("%d%d", &n, &k), n|k) {
		int w = 0;
		for (int i=0; i<k; ++i) {
			int t;
			scanf("%d", &t);
			if (t == 0)
				w = 1;
			else
				v[i-w] = t;
		}
		std::sort(v, v+k-w);
		dp[0] = 1;
		for (int i=1; i<k-w; ++i)
			dp[i] = v[i]-v[i-1]==1 ? dp[i-1]+1 : 1;
		bool used = false;
		if (w) {
			dp2[0] = 1, dp2[k-w] = 1000011;
			for (int i=1; i<k-w; ++i) {
				if (v[i] - v[i-1] == 1) {
					dp2[i] = dp2[i-1]+1;
				}
				else {
					if (v[i] - v[i-1] == 2) {
						dp2[i] = dp[i-1] + 2;
						used = true;
					}
					else {
						dp2[i] = 1;
					}
				}
			}
		}
		printf("%d\n", std::max(*std::max_element(dp, dp+k-w), *std::max_element(dp2, dp2+k-w)+!used));
	}
	return 0;
}
```