#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {

  while( true ) {

    long long int n, k;
    cin >> n >> k;
    if ( n == 0 ) break;

    bool w = false;

    vector< long long int > c;
    for ( long long int i = 0; i < k; i++ ) {
      long long int in;
      cin >> in;
      if ( in == 0 ) {
	w = true;
      }else {
	c.push_back( in );
      }
    }

    c.push_back( n + 100 );

    sort( c.begin(), c.end() );

    long long int ans = 0;
    long long int h[2] = {0};
    long long int u = -10;

    for ( long long int i = 0; i < c.size(); i++ ) {
      if ( u + 1 == c[i] ) {
	h[0]++;
      }else if ( u + 2 == c[i] && w == true ) {
	ans = max( ans, h[0] + h[1] );
	h[1] = h[0] + 1;
	h[0] = 1;
      }else {
	ans = max( ans, h[0] + h[1] );
	h[0] = 1;
	h[1] = 0;
      }
      u = c[i];
    }

    cout << ans << endl;

  }

  return 0;

}
### 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 <vector>
#include <algorithm>
using namespace std;

int main() {

  while( true ) {

    long long int n, k;
    cin >> n >> k;
    if ( n == 0 ) break;

    bool w = false;

    vector< long long int > c;
    for ( long long int i = 0; i < k; i++ ) {
      long long int in;
      cin >> in;
      if ( in == 0 ) {
	w = true;
      }else {
	c.push_back( in );
      }
    }

    c.push_back( n + 100 );

    sort( c.begin(), c.end() );

    long long int ans = 0;
    long long int h[2] = {0};
    long long int u = -10;

    for ( long long int i = 0; i < c.size(); i++ ) {
      if ( u + 1 == c[i] ) {
	h[0]++;
      }else if ( u + 2 == c[i] && w == true ) {
	ans = max( ans, h[0] + h[1] );
	h[1] = h[0] + 1;
	h[0] = 1;
      }else {
	ans = max( ans, h[0] + h[1] );
	h[0] = 1;
	h[1] = 0;
      }
      u = c[i];
    }

    cout << ans << endl;

  }

  return 0;

}
```