#include<cstdio>
#include<cstring>
#include<algorithm>
int main(void){
  int n, k, m;
  int t1, t2, ans;
  bool c[100010];
  bool f;
  for( ; ; ){
    scanf("%d %d", &n, &k);
    if(!(n + k)) break;
    for(int i = 0;i <= n; i++) c[i] = false;
    for(int i = 0;i < k; i++){
      scanf("%d", &m);
      c[m] = true;
    }
    f = c[0]? true : false;
    t1 = f? 1 : 0;
    t2 = ans = 0;
    if(f){
      for(int i = 1;i <= n; i++){
	if(c[i]){
	  t1++; t2++;
	}
	else if(!f && i >= 2 && c[i - 1] && c[i + 1] && i < n){
	  t1++; t2 = 0; f = true;
	}
	if(!c[i] && (f || i < 2) || i == n){
	  if(!f && c[i] < n) t1++;
	  ans = std::max(ans, t1);
	  if(f){
	    t1 = t2; t2 = 0;
	  } else {
	    t1 = t2 = 0;
	  }
	  f = c[0]? true : false;
	  if(c[i + 1] == true){
	    t1++; f = true;
	  }
	}
      }
    } else {
      for(int i = 1;i <= n; i++){
	if(c[i]) t1++;
	if(!c[i] || i == n){
	  ans = std::max(ans, t1);
	  t1 = 0;
	}
      }
    }
    printf("%d\n", ans);
  }
}

### 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<cstring>
#include<algorithm>
int main(void){
  int n, k, m;
  int t1, t2, ans;
  bool c[100010];
  bool f;
  for( ; ; ){
    scanf("%d %d", &n, &k);
    if(!(n + k)) break;
    for(int i = 0;i <= n; i++) c[i] = false;
    for(int i = 0;i < k; i++){
      scanf("%d", &m);
      c[m] = true;
    }
    f = c[0]? true : false;
    t1 = f? 1 : 0;
    t2 = ans = 0;
    if(f){
      for(int i = 1;i <= n; i++){
	if(c[i]){
	  t1++; t2++;
	}
	else if(!f && i >= 2 && c[i - 1] && c[i + 1] && i < n){
	  t1++; t2 = 0; f = true;
	}
	if(!c[i] && (f || i < 2) || i == n){
	  if(!f && c[i] < n) t1++;
	  ans = std::max(ans, t1);
	  if(f){
	    t1 = t2; t2 = 0;
	  } else {
	    t1 = t2 = 0;
	  }
	  f = c[0]? true : false;
	  if(c[i + 1] == true){
	    t1++; f = true;
	  }
	}
      }
    } else {
      for(int i = 1;i <= n; i++){
	if(c[i]) t1++;
	if(!c[i] || i == n){
	  ans = std::max(ans, t1);
	  t1 = 0;
	}
      }
    }
    printf("%d\n", ans);
  }
}

```