#include<bits/stdc++.h>
using namespace std;

#define rep(i, n) for(int i=0; i<n; i++)

int d[111111];
int n, k;

int main()
{
  while(cin >> n >> k, n){
    rep(i, k) cin >> d[i];
    sort(d, d + k);

    bool ok = false;
    int p = 0;
    int res = 0;
    if(d[0] == 0) ok = true,  p += 1;
    while(p < k){
      int cnt = 1;
      while(p + 1 < k && d[p + 1] - d[p] == 1) p += 1,  cnt += 1;
      int pp = p + 1;
      if(ok && d[p + 1] - d[p] == 2){
        cnt += 2;
        p += 1;
        while(p + 1 < k && d[p + 1] - d[p] == 1) p += 1,  cnt += 1;
      }
      p = pp;
      res = max(res, cnt);
    }

    cout << res << endl;
  }

  return 0;
}
### 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>
using namespace std;

#define rep(i, n) for(int i=0; i<n; i++)

int d[111111];
int n, k;

int main()
{
  while(cin >> n >> k, n){
    rep(i, k) cin >> d[i];
    sort(d, d + k);

    bool ok = false;
    int p = 0;
    int res = 0;
    if(d[0] == 0) ok = true,  p += 1;
    while(p < k){
      int cnt = 1;
      while(p + 1 < k && d[p + 1] - d[p] == 1) p += 1,  cnt += 1;
      int pp = p + 1;
      if(ok && d[p + 1] - d[p] == 2){
        cnt += 2;
        p += 1;
        while(p + 1 < k && d[p + 1] - d[p] == 1) p += 1,  cnt += 1;
      }
      p = pp;
      res = max(res, cnt);
    }

    cout << res << endl;
  }

  return 0;
}
```