#include<iostream>
#include<string>
#include<algorithm>
#define int long long
using namespace std;
int ok[213456];
signed main() {
	for (int y = 0; y < 10; y++) {
		for (int z = 0; z < 213456; z++) {
			ok[z] = 0;
		}
		int n, k, a, cnt = 0, sum = 0, ans = 0; cin >> n >> k;
		if (n == 0 && k == 0) { continue; }
		int mae = 0, ato = 0, husi = 0;
		for (int h = 0; h < k; h++) {
			cin >> a; ok[a] = 1;
			if (a == 0) { cnt++; }
		}
		if (cnt == 0) {
			for (int h = 1; h <= n; h++) {
				if (ok[h] == 1) { sum++; }
				else {
					ans = max(sum, ans); sum = 0;
				}
			}
		}
		else {
			for (int h = 1; h <= n; h++) {
				if (ok[h] == 1) {
					mae++; ato++;
				}
				else {
					if (husi % 2 == 0) { ans = max(ans, mae); mae = 0; ato++; }
					else { ans = max(ans, ato); mae++; ato = 0; }
					husi++;
				}
				ans = max(ans, max(mae, ato));
			}
		}
		cout << ans << 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<iostream>
#include<string>
#include<algorithm>
#define int long long
using namespace std;
int ok[213456];
signed main() {
	for (int y = 0; y < 10; y++) {
		for (int z = 0; z < 213456; z++) {
			ok[z] = 0;
		}
		int n, k, a, cnt = 0, sum = 0, ans = 0; cin >> n >> k;
		if (n == 0 && k == 0) { continue; }
		int mae = 0, ato = 0, husi = 0;
		for (int h = 0; h < k; h++) {
			cin >> a; ok[a] = 1;
			if (a == 0) { cnt++; }
		}
		if (cnt == 0) {
			for (int h = 1; h <= n; h++) {
				if (ok[h] == 1) { sum++; }
				else {
					ans = max(sum, ans); sum = 0;
				}
			}
		}
		else {
			for (int h = 1; h <= n; h++) {
				if (ok[h] == 1) {
					mae++; ato++;
				}
				else {
					if (husi % 2 == 0) { ans = max(ans, mae); mae = 0; ato++; }
					else { ans = max(ans, ato); mae++; ato = 0; }
					husi++;
				}
				ans = max(ans, max(mae, ato));
			}
		}
		cout << ans << endl;
	}
	return 0;
}

```