// http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=0517
// ???????????????????????¨????????????????????????????????????????????£????????§?????????????????§???????£???????????????????
// ????????????????????????????????£?????°????????????????????????????????????

#include <iostream>
using namespace std;

bool paper[100100];

int main() {
  int n, k;
  while (cin >> n >> k && n && k) {
    fill(paper, paper+n+100, false);
    int x;
    for (auto i=0; i<k; i++) {
      cin >> x;
      paper[x] = true;
    }
    int white = (paper[0] ? 1 : 0);
    int f = 0, l = 0;
    int cnt = 0;
    int ans = 0;
    while (l <= n) {
      if (cnt <= white) {
        if (!paper[++f]) {
          cnt++;
        }
      } else {
        // cerr << f << " " << l << endl;
        ans = max(ans, f-l-1);
        if (!paper[++l]) cnt--;
      }
    }
    cout << ans << endl;
  }
}
### Prompt

Develop a solution in Cpp to the problem described below:

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
// http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=0517
// ???????????????????????¨????????????????????????????????????????????£????????§?????????????????§???????£???????????????????
// ????????????????????????????????£?????°????????????????????????????????????

#include <iostream>
using namespace std;

bool paper[100100];

int main() {
  int n, k;
  while (cin >> n >> k && n && k) {
    fill(paper, paper+n+100, false);
    int x;
    for (auto i=0; i<k; i++) {
      cin >> x;
      paper[x] = true;
    }
    int white = (paper[0] ? 1 : 0);
    int f = 0, l = 0;
    int cnt = 0;
    int ans = 0;
    while (l <= n) {
      if (cnt <= white) {
        if (!paper[++f]) {
          cnt++;
        }
      } else {
        // cerr << f << " " << l << endl;
        ans = max(ans, f-l-1);
        if (!paper[++l]) cnt--;
      }
    }
    cout << ans << endl;
  }
}
```