#include <iostream>
#include <algorithm>
using namespace std;
int n=0, k=0, a[100000] = {}, sam, b[100000] = {}, roop = 0, save[100000] = {0}, ans[100000] = {}, w = 0;
int main(void){
	while (1){
		int n=0, k=0, a[100000] = {}, sam, b[100000] = {}, roop = 0, save[100000] = {0}, ans[100000] = {}, w = 0;
		cin >> n >> k;
		if (n == 0 && k == 0)
			break;
		for (int i = 0; i<k; i++){
			cin >> a[i];
		}
		sort(a, a + k);
		for (int i = 0; i<k; i++){
			if (a[i + 1] - a[i] == 1){
				sam++;
			}
			else if (a[i + 1] - a[i] != 1){
				b[roop] = sam+1;
				if(a[0]==0){
					if (a[i + 1] - a[i] == 2){
						save[w] = roop;
						w++;
					}
				}
				sam = 0;
				roop++;
			}
		}
		for (int i = 0; i <= roop; i++){
			if (save[i] != 0){
				ans[i] = b[save[i]];
				ans[i]+= b[save[i] + 1] + 1;
			}
		}
		sort(b, b + roop+1);
		sort(ans, ans + roop+1);
		if (ans[roop]>b[roop])
		cout << ans[roop] << endl;
		if (ans[roop] <= b[roop]){
			if(a[0]==0){
				cout << b[roop]+1 << endl;
			}
			else{
			cout << b[roop] << endl;
			}
		}
	}
	return 0;
}
### Prompt

Your task is to create a CPP solution to 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 <algorithm>
using namespace std;
int n=0, k=0, a[100000] = {}, sam, b[100000] = {}, roop = 0, save[100000] = {0}, ans[100000] = {}, w = 0;
int main(void){
	while (1){
		int n=0, k=0, a[100000] = {}, sam, b[100000] = {}, roop = 0, save[100000] = {0}, ans[100000] = {}, w = 0;
		cin >> n >> k;
		if (n == 0 && k == 0)
			break;
		for (int i = 0; i<k; i++){
			cin >> a[i];
		}
		sort(a, a + k);
		for (int i = 0; i<k; i++){
			if (a[i + 1] - a[i] == 1){
				sam++;
			}
			else if (a[i + 1] - a[i] != 1){
				b[roop] = sam+1;
				if(a[0]==0){
					if (a[i + 1] - a[i] == 2){
						save[w] = roop;
						w++;
					}
				}
				sam = 0;
				roop++;
			}
		}
		for (int i = 0; i <= roop; i++){
			if (save[i] != 0){
				ans[i] = b[save[i]];
				ans[i]+= b[save[i] + 1] + 1;
			}
		}
		sort(b, b + roop+1);
		sort(ans, ans + roop+1);
		if (ans[roop]>b[roop])
		cout << ans[roop] << endl;
		if (ans[roop] <= b[roop]){
			if(a[0]==0){
				cout << b[roop]+1 << endl;
			}
			else{
			cout << b[roop] << endl;
			}
		}
	}
	return 0;
}
```