#include <iostream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <cfloat>
using namespace std;

int main()
{
    for(;;){
        int n, k;
        cin >> n >> k;
        if(n == 0)
            return 0;

        vector<bool> card(n+1, false);
        for(int i=0; i<k; ++i){
            int a;
            cin >> a;
            card[a] = true;
        }

        int ret = 0;
        int l1 = 0;
        int l2 = 0;
        for(int i=1; i<=n; ++i){
            if(card[i]){
                ++ l1;
                ++ l2;
            }else{
                l2 = l1 + 1;
                l1 = 0;
            }
            ret = max(ret, l1);
            if(card[0])
                ret = max(ret, l2);
        }
        cout << ret << endl;
    }
}
### Prompt

In cpp, your task is to solve 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 <sstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <cfloat>
using namespace std;

int main()
{
    for(;;){
        int n, k;
        cin >> n >> k;
        if(n == 0)
            return 0;

        vector<bool> card(n+1, false);
        for(int i=0; i<k; ++i){
            int a;
            cin >> a;
            card[a] = true;
        }

        int ret = 0;
        int l1 = 0;
        int l2 = 0;
        for(int i=1; i<=n; ++i){
            if(card[i]){
                ++ l1;
                ++ l2;
            }else{
                l2 = l1 + 1;
                l1 = 0;
            }
            ret = max(ret, l1);
            if(card[0])
                ret = max(ret, l2);
        }
        cout << ret << endl;
    }
}
```