#include<iostream>
#include<algorithm>
using namespace std;
int a[100000];
int main() {
	int n, k;
	while (cin >> n >> k&&n != 0 && k != 0) {
		int sum = 1, c = 0;
		fill(a, a + n, false);
		for (int i = 0; i < k; i++) {
			cin >> sum;
			if (sum == 0)
				c++;
			else a[i - c] = sum;
		}
		sum = 0;
		sort(a, a + k - c);
		for (int i = 0; i < k - c; i++) {
			int b = c, ne = a[i], e = i + 1;
			ne++;
			while (ne == a[e]) {
				e++;
				ne++;
			}
			if (c == 1) {
				ne++;
				while (ne == a[e]) {
					ne++;
					e++;
				}
			}
			sum = max(sum, ne - a[i]);
		}
		cout << sum << endl;
	}
}
### 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<algorithm>
using namespace std;
int a[100000];
int main() {
	int n, k;
	while (cin >> n >> k&&n != 0 && k != 0) {
		int sum = 1, c = 0;
		fill(a, a + n, false);
		for (int i = 0; i < k; i++) {
			cin >> sum;
			if (sum == 0)
				c++;
			else a[i - c] = sum;
		}
		sum = 0;
		sort(a, a + k - c);
		for (int i = 0; i < k - c; i++) {
			int b = c, ne = a[i], e = i + 1;
			ne++;
			while (ne == a[e]) {
				e++;
				ne++;
			}
			if (c == 1) {
				ne++;
				while (ne == a[e]) {
					ne++;
					e++;
				}
			}
			sum = max(sum, ne - a[i]);
		}
		cout << sum << endl;
	}
}
```