#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;

ll n, k, a, d[100002];

int main() {
  while (1) {
    scanf("%lld%lld", &n, &k);
    if (n == 0) break;
    for (int i = 0; i <= n + 2; i++) d[i] = 0;
    bool flag = false;
    ll ans = 0;
    for (ll i = 0; i < k; i++) {
      scanf("%lld", &a);
      if (a == 0) { flag = true; continue; }
      d[a] = 1;
    }
    //for (ll i = 0; i < n + 2; i++) printf("%lld ",d[i]); printf("\n");
    ll counter = 0, temp = -1;
    for (ll i = 1; i <= n + 1; i++) {
      if (d[i] == 1) counter++;
      else if (d[i - 1] == 1) {
        ans = max(ans, counter + temp + 1);
        if (flag && d[i + 1] == 1) temp = counter;
        else temp = -1;
        counter = 0;
      } else temp = -1, counter = 0;
    }
    if (n == k) printf("%lld\n", n);
    else printf("%lld\n", ans);
  }
}


### 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
#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;

ll n, k, a, d[100002];

int main() {
  while (1) {
    scanf("%lld%lld", &n, &k);
    if (n == 0) break;
    for (int i = 0; i <= n + 2; i++) d[i] = 0;
    bool flag = false;
    ll ans = 0;
    for (ll i = 0; i < k; i++) {
      scanf("%lld", &a);
      if (a == 0) { flag = true; continue; }
      d[a] = 1;
    }
    //for (ll i = 0; i < n + 2; i++) printf("%lld ",d[i]); printf("\n");
    ll counter = 0, temp = -1;
    for (ll i = 1; i <= n + 1; i++) {
      if (d[i] == 1) counter++;
      else if (d[i - 1] == 1) {
        ans = max(ans, counter + temp + 1);
        if (flag && d[i + 1] == 1) temp = counter;
        else temp = -1;
        counter = 0;
      } else temp = -1, counter = 0;
    }
    if (n == k) printf("%lld\n", n);
    else printf("%lld\n", ans);
  }
}


```