#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)


int n, k;
bool card[100001];

int main() {
	while (true) {
		cin >> n >> k;
		if (n == 0 && k == 0) break;
		REP(i, n + 1) card[i] = false;

		REP(i, k) {
			int a;
			scanf("%d", &a);
			card[a] = true;
		}
		int l = 1, r = 1, ans = 0, magic = 0;

		while (true) {
			if (r > n) { ans = max(ans, r - l); break; }

			if (!card[r]) {
				if (magic == 0 && card[0]) {
					magic = r;
				} else if (magic != 0) {
					ans = max(ans, r - l);
					l = magic + 1;
					magic = r;
				} else {
					ans = max(ans, r - l);
					l = r + 1;
				}
			}
			r++;
		}
		cout << ans << endl;
	}
	return 0;
}
### Prompt

Create a solution in CPP for 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 <cstdio>
#include <algorithm>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)


int n, k;
bool card[100001];

int main() {
	while (true) {
		cin >> n >> k;
		if (n == 0 && k == 0) break;
		REP(i, n + 1) card[i] = false;

		REP(i, k) {
			int a;
			scanf("%d", &a);
			card[a] = true;
		}
		int l = 1, r = 1, ans = 0, magic = 0;

		while (true) {
			if (r > n) { ans = max(ans, r - l); break; }

			if (!card[r]) {
				if (magic == 0 && card[0]) {
					magic = r;
				} else if (magic != 0) {
					ans = max(ans, r - l);
					l = magic + 1;
					magic = r;
				} else {
					ans = max(ans, r - l);
					l = r + 1;
				}
			}
			r++;
		}
		cout << ans << endl;
	}
	return 0;
}
```