#include<cstdio>
#include<algorithm>
using namespace std;
int main(){

  int n,m,k,ans,a[100001];
  int f1,f2,s1,s2;
  scanf("%d %d",&n,&m);
  while(n != 0 && m != 0){
    ans = 0;
    fill(a,a+100001,0);
    for(int i=0;i<m;i++){
      scanf("%d",&k);
      a[k] = 1;
    }
    
    f1 = f2 = s1 = s2 = 0;
    for(int i=1;i<=n;i++){
      if(f1 == 0 && f2 == 0) f2 = 1;    
      if(a[i] == 1){
	s1++;
	s2++;
      }
      else {
	if(f1 == 0 && a[0] == 1){
	  f1++;
	  s1++;
	} else {
	  ans = max(ans,s1);
	  f1 = 0;
	  s1 = 0;
	}
	if(f2 == 0 && a[0] == 1){
	  f2++;
	  s2++;
	} else {
	  ans = max(ans,s2);
	  f2 = 0;
	  s2 = 0;
	}
      }
      ans = max(ans,s1);
      ans = max(ans,s2);
    }
    printf("%d\n",ans);
    scanf("%d %d",&n,&m);
  }
  return (0);
}
      
### Prompt

Please formulate 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<cstdio>
#include<algorithm>
using namespace std;
int main(){

  int n,m,k,ans,a[100001];
  int f1,f2,s1,s2;
  scanf("%d %d",&n,&m);
  while(n != 0 && m != 0){
    ans = 0;
    fill(a,a+100001,0);
    for(int i=0;i<m;i++){
      scanf("%d",&k);
      a[k] = 1;
    }
    
    f1 = f2 = s1 = s2 = 0;
    for(int i=1;i<=n;i++){
      if(f1 == 0 && f2 == 0) f2 = 1;    
      if(a[i] == 1){
	s1++;
	s2++;
      }
      else {
	if(f1 == 0 && a[0] == 1){
	  f1++;
	  s1++;
	} else {
	  ans = max(ans,s1);
	  f1 = 0;
	  s1 = 0;
	}
	if(f2 == 0 && a[0] == 1){
	  f2++;
	  s2++;
	} else {
	  ans = max(ans,s2);
	  f2 = 0;
	  s2 = 0;
	}
      }
      ans = max(ans,s1);
      ans = max(ans,s2);
    }
    printf("%d\n",ans);
    scanf("%d %d",&n,&m);
  }
  return (0);
}
      
```