#include<iostream>
#include<vector>

using namespace std;
int legth(int a){

}
int main(){
    int x,y,a,b=0,c=0,d=0,e=0,ans=0,k=0;
    int g[101000],r[101000];
    while(1){
            fill(g,g+101000,0);
    fill(r,r+101000,0);
    cin >> x >> y;
    if(x==0&&y==0)break;
    for(int u=0;u<y;u++){
        cin >> a;
        g[a]=1;
    }

    for(int y=1;y<=x;y++){
            if(g[y]==1){
                b++;
                k=0;
                if(y==x){
                     r[y]=b;
    r[y-b-1]=b;
                }
            }else{
        if(k==0){
        r[y]=b;
    r[y-b+1]=b;
       }
        k=1;
    b=0;
            }

        if(c<b)c=b;
    }
    ans=c;
    if(g[0]==1){

        for(int j=1;j<x+1;j++){
        if(g[j]!=1){

                d=r[j]+r[j+2]+1;

        if(e<d)e=d;
    }
        }
    }
    if(ans<e)ans=e;


    b=0;
    cout << ans << endl;
    c=0;
    ans=0;
    }
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<iostream>
#include<vector>

using namespace std;
int legth(int a){

}
int main(){
    int x,y,a,b=0,c=0,d=0,e=0,ans=0,k=0;
    int g[101000],r[101000];
    while(1){
            fill(g,g+101000,0);
    fill(r,r+101000,0);
    cin >> x >> y;
    if(x==0&&y==0)break;
    for(int u=0;u<y;u++){
        cin >> a;
        g[a]=1;
    }

    for(int y=1;y<=x;y++){
            if(g[y]==1){
                b++;
                k=0;
                if(y==x){
                     r[y]=b;
    r[y-b-1]=b;
                }
            }else{
        if(k==0){
        r[y]=b;
    r[y-b+1]=b;
       }
        k=1;
    b=0;
            }

        if(c<b)c=b;
    }
    ans=c;
    if(g[0]==1){

        for(int j=1;j<x+1;j++){
        if(g[j]!=1){

                d=r[j]+r[j+2]+1;

        if(e<d)e=d;
    }
        }
    }
    if(ans<e)ans=e;


    b=0;
    cout << ans << endl;
    c=0;
    ans=0;
    }
return 0;
}
```