#include<iostream>
#include<cstdio>
using namespace std;

int main(){
    int n,k;
    while(cin>>n>>k,n||k){
        bool series[100001]={},flag,ansflag;
        int ans,input,lastedge,lastlen,edge,len,mxlen;
        for(int i=0;i<k;i++){
            cin>>input;
            series[input]=true;
        }
        ans=0;lastedge=-1;
        for(int i=1;i<=n;i++){
            if(series[i]){
                edge=i;
                for(len=0;i<=n && series[i];i++){
                    len++;
                }
                if(series[0] && lastedge+2==edge){
                    mxlen=len+lastlen+1;
                    flag=true;
                }
                else{
                    mxlen=len;
                    flag=false;
                }
                if(mxlen>ans){
                    ans=mxlen;
                    ansflag=flag;
                }
                lastlen=len;
                lastedge=i-1;
            }
        }
        if(series[0] && !ansflag) ans++;
        printf("%d\n",ans);
    }
    return 0;
}
### Prompt

Generate 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<cstdio>
using namespace std;

int main(){
    int n,k;
    while(cin>>n>>k,n||k){
        bool series[100001]={},flag,ansflag;
        int ans,input,lastedge,lastlen,edge,len,mxlen;
        for(int i=0;i<k;i++){
            cin>>input;
            series[input]=true;
        }
        ans=0;lastedge=-1;
        for(int i=1;i<=n;i++){
            if(series[i]){
                edge=i;
                for(len=0;i<=n && series[i];i++){
                    len++;
                }
                if(series[0] && lastedge+2==edge){
                    mxlen=len+lastlen+1;
                    flag=true;
                }
                else{
                    mxlen=len;
                    flag=false;
                }
                if(mxlen>ans){
                    ans=mxlen;
                    ansflag=flag;
                }
                lastlen=len;
                lastedge=i-1;
            }
        }
        if(series[0] && !ansflag) ans++;
        printf("%d\n",ans);
    }
    return 0;
}
```