#include<bits/stdc++.h>
using namespace std;
int main(){
  int n,k;
  while(cin >> n >> k,n){
    vector<int> mp(n+1,false);
    for(int i=0;i<k;++i){
      int tmp;
      cin >> tmp;
      mp[tmp] = true;
    }
    vector<int> vec;
    vec.push_back(mp[1]);
    for(int i=2;i<n+1;++i){
      if(mp[i]&&mp[i-1]){
        vec.back()++;
        continue;
      }
      vec.push_back(mp[i]);
    }
    int ans = 0;
    if(!mp[0]||vec.size()<3){
      cout << *max_element(vec.begin(),vec.end()) << endl;
      continue;
    }
    for(int i=0;i<(int)vec.size()-2;++i){
      ans = max(ans,vec[i]+vec[i+2]+1);
    }
    cout << ans << endl;
  }
}

### 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<bits/stdc++.h>
using namespace std;
int main(){
  int n,k;
  while(cin >> n >> k,n){
    vector<int> mp(n+1,false);
    for(int i=0;i<k;++i){
      int tmp;
      cin >> tmp;
      mp[tmp] = true;
    }
    vector<int> vec;
    vec.push_back(mp[1]);
    for(int i=2;i<n+1;++i){
      if(mp[i]&&mp[i-1]){
        vec.back()++;
        continue;
      }
      vec.push_back(mp[i]);
    }
    int ans = 0;
    if(!mp[0]||vec.size()<3){
      cout << *max_element(vec.begin(),vec.end()) << endl;
      continue;
    }
    for(int i=0;i<(int)vec.size()-2;++i){
      ans = max(ans,vec[i]+vec[i+2]+1);
    }
    cout << ans << endl;
  }
}

```