#include <cstdio>
#include <algorithm>

using namespace std;

int n,k;
int c[100001];

int main(){
	while(scanf("%d%d",&n,&k), n != 0){
		for(int i = 0; i < k; i++){
			scanf("%d",&c[i]);
		}
		sort(c,c+k);
		c[n] = 100000000;
		
		int mx = 1;
		if(c[0] == 0){
			int st = 0;
			int tmp = 0;
			int pos = 1;
			for(int i = 1; i <= n; i++){
				if (c[pos] == i){
					pos++;
				}
				else{ // c[pos] > i
					st = tmp;
					tmp = i;
				}
				mx = i - st > mx ? i - st : mx;
			}
		}
		else{
			int st = 0;
			int pos = 0;
			for(int i = 1; i <= n; i++){
				if (c[pos] == i){
					pos++;
				}
				else{ // c[pos] > i
					st = i;
				}
				mx = i - st > mx ? i - st : mx;
			}
		}
		printf("%d\n",mx);
	}
	return 0;
}


### 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 <cstdio>
#include <algorithm>

using namespace std;

int n,k;
int c[100001];

int main(){
	while(scanf("%d%d",&n,&k), n != 0){
		for(int i = 0; i < k; i++){
			scanf("%d",&c[i]);
		}
		sort(c,c+k);
		c[n] = 100000000;
		
		int mx = 1;
		if(c[0] == 0){
			int st = 0;
			int tmp = 0;
			int pos = 1;
			for(int i = 1; i <= n; i++){
				if (c[pos] == i){
					pos++;
				}
				else{ // c[pos] > i
					st = tmp;
					tmp = i;
				}
				mx = i - st > mx ? i - st : mx;
			}
		}
		else{
			int st = 0;
			int pos = 0;
			for(int i = 1; i <= n; i++){
				if (c[pos] == i){
					pos++;
				}
				else{ // c[pos] > i
					st = i;
				}
				mx = i - st > mx ? i - st : mx;
			}
		}
		printf("%d\n",mx);
	}
	return 0;
}


```