#include<vector>
#include<list>
#include<algorithm>
#include<iostream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
using namespace std;
int main(){
  int i,j,k;
  int a[100001],l,m,n;
  int mx;
  while(cin>>n>>m&&n+m){
    memset(a,0,sizeof(a));
    for(i=0;i<m;i++){
      cin>>l;
      a[l]=1;
    }
    mx=1;
    if(a[0]){
      for(i=1;i<n+1;i=j){
	for(;i<n+1&&a[i]==0;i++);
	for(j=i;j<n+1&&a[j];j++);
	if(j<n+1&&a[j+1]){
	  for(k=j+1;k<n+1&&a[k];k++);
	  if(k-i>mx)
	    mx=k-i;
	}else{
	  if(j-i>mx)
	    mx=j-i;
	}
      }
    }else{
      for(i=1;i<n+1;i=j){
	for(;i<n+1&&a[i]==0;i++);
	for(j=i;j<n+1&&a[j];j++);
	if(j-i>mx)
	  mx=j-i;
      }
    }
    cout<<mx<<endl;
  }
  return 0;
}
### Prompt

Your challenge is to write 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<vector>
#include<list>
#include<algorithm>
#include<iostream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
using namespace std;
int main(){
  int i,j,k;
  int a[100001],l,m,n;
  int mx;
  while(cin>>n>>m&&n+m){
    memset(a,0,sizeof(a));
    for(i=0;i<m;i++){
      cin>>l;
      a[l]=1;
    }
    mx=1;
    if(a[0]){
      for(i=1;i<n+1;i=j){
	for(;i<n+1&&a[i]==0;i++);
	for(j=i;j<n+1&&a[j];j++);
	if(j<n+1&&a[j+1]){
	  for(k=j+1;k<n+1&&a[k];k++);
	  if(k-i>mx)
	    mx=k-i;
	}else{
	  if(j-i>mx)
	    mx=j-i;
	}
      }
    }else{
      for(i=1;i<n+1;i=j){
	for(;i<n+1&&a[i]==0;i++);
	for(j=i;j<n+1&&a[j];j++);
	if(j-i>mx)
	  mx=j-i;
      }
    }
    cout<<mx<<endl;
  }
  return 0;
}
```