#include <bits/stdc++.h>
using namespace std;

int main()
{
	cin.sync_with_stdio(false);
	int n, k;
	while (cin >> n >> k, n | k) {
		bool e = false;
		vector<int> a(k);
		for (int i = 0; i < k; i++) {
			cin >> a[i];
			if (a[i] == 0) {
				e = true;
				a[i] = -10;
			}
		}
		sort(a.begin(), a.end());
		int t1 = 1, t2 = 1, res = 1;
		for (int i = 1; i < k; i++) {
			if (a[i] - a[i - 1] == 1) {
				t1++;
				t2++;
			}
			else if (a[i] - a[i - 1] == 2) {
				t2 = t1 + 2;
				t1 = 1;
			}
			else {
				t1 = t2 = 1;
			}
			res = max(res, e ? t2 : t1);
		}
		cout << res << endl;
	}
	return 0;
}


### Prompt

In CPP, your task is to solve 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
#include <bits/stdc++.h>
using namespace std;

int main()
{
	cin.sync_with_stdio(false);
	int n, k;
	while (cin >> n >> k, n | k) {
		bool e = false;
		vector<int> a(k);
		for (int i = 0; i < k; i++) {
			cin >> a[i];
			if (a[i] == 0) {
				e = true;
				a[i] = -10;
			}
		}
		sort(a.begin(), a.end());
		int t1 = 1, t2 = 1, res = 1;
		for (int i = 1; i < k; i++) {
			if (a[i] - a[i - 1] == 1) {
				t1++;
				t2++;
			}
			else if (a[i] - a[i - 1] == 2) {
				t2 = t1 + 2;
				t1 = 1;
			}
			else {
				t1 = t2 = 1;
			}
			res = max(res, e ? t2 : t1);
		}
		cout << res << endl;
	}
	return 0;
}


```