#include <bits/stdc++.h>
const int INF=1e9,MOD=1e9+7;
const long long LINF=1e18;
using namespace std;
#define int long long
//template
//main
signed main(){
  int N,X;cin>>N>>X;
  std::vector<int> ans;
  while(N||X){
    std::vector<int> v(X);
    for(int i=0;i<X;i++)cin>>v[i];
    sort(v.begin(),v.end());
    if(v[0]){
      int res=0,tmp=0;
      for(int i=1;i<X;i++){
        if(v[i]==v[i-1]+1){tmp++;res=max(res,tmp);}
        else tmp=0;
      }
      ans.push_back(res+1);
    }
    else{
      int res=0,tmp=0,tmp2=0;
      for(int i=2;i<X;i++){
        if(v[i]==v[i-1]+1){
          tmp++;tmp2++;res=max(tmp2,res);
          res=max(res,tmp+1);
        }
        else if(v[i]==v[i-1]+2){
          tmp2=tmp+2;
          tmp=0;
          res=max(res,tmp2);
        }
        else{tmp=tmp2=0;}
      }
      if(X>=2&&res<=1)res=1;
      ans.push_back(res+1);
    }
    cin>>N>>X;
  }
  for(int p:ans)cout<<p<<endl;
}


### Prompt

Construct a cpp code solution to the problem outlined:

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 <bits/stdc++.h>
const int INF=1e9,MOD=1e9+7;
const long long LINF=1e18;
using namespace std;
#define int long long
//template
//main
signed main(){
  int N,X;cin>>N>>X;
  std::vector<int> ans;
  while(N||X){
    std::vector<int> v(X);
    for(int i=0;i<X;i++)cin>>v[i];
    sort(v.begin(),v.end());
    if(v[0]){
      int res=0,tmp=0;
      for(int i=1;i<X;i++){
        if(v[i]==v[i-1]+1){tmp++;res=max(res,tmp);}
        else tmp=0;
      }
      ans.push_back(res+1);
    }
    else{
      int res=0,tmp=0,tmp2=0;
      for(int i=2;i<X;i++){
        if(v[i]==v[i-1]+1){
          tmp++;tmp2++;res=max(tmp2,res);
          res=max(res,tmp+1);
        }
        else if(v[i]==v[i-1]+2){
          tmp2=tmp+2;
          tmp=0;
          res=max(res,tmp2);
        }
        else{tmp=tmp2=0;}
      }
      if(X>=2&&res<=1)res=1;
      ans.push_back(res+1);
    }
    cin>>N>>X;
  }
  for(int p:ans)cout<<p<<endl;
}


```