#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

int main() {

  while (true) {
	int n, k;
	scanf( "%d %d\n", &n, &k );
	if ( n == 0 && k == 0 ) break;

	vector<int> v( k );
	for ( int i = 0; i < k; i++ ) {
	  int val;
	  scanf( "%d\n", &val );
	  v[ i ] = val;
	}
	
	sort( v.begin(), v.end() );
	bool hasWhite = ( v[ 0 ] == 0 );
	if ( hasWhite ) {
	  
	}
	
	vector<pair<int, int>> ps;
	int start = v[ 0 ];
	int before = v[ 0 ];
	for ( int i = 1; i < k; i++ ) {
	  if ( v[ i ] - before == 1 ) {
		before = v[ i ];
	  } else {
		ps.push_back( make_pair( start, before ) );
		start = before = v[ i ];
	  }
	}
	ps.push_back( make_pair( start, before ) );

	int maxSize = 0;
	for ( auto p : ps ) {
	  maxSize = max( maxSize, p.second - p.first + 1 );
	}

	if ( hasWhite ) {
	  for ( int i = 0; i < ps.size() - 1; i++ ) {
		if ( ps[ i + 1 ].first - ps[ i ].second == 2 ) {
		  maxSize = max( maxSize, ps[ i + 1 ].second - ps[ i ].first + 1 );
		}
	  }
	}
	cout << maxSize << 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 <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

int main() {

  while (true) {
	int n, k;
	scanf( "%d %d\n", &n, &k );
	if ( n == 0 && k == 0 ) break;

	vector<int> v( k );
	for ( int i = 0; i < k; i++ ) {
	  int val;
	  scanf( "%d\n", &val );
	  v[ i ] = val;
	}
	
	sort( v.begin(), v.end() );
	bool hasWhite = ( v[ 0 ] == 0 );
	if ( hasWhite ) {
	  
	}
	
	vector<pair<int, int>> ps;
	int start = v[ 0 ];
	int before = v[ 0 ];
	for ( int i = 1; i < k; i++ ) {
	  if ( v[ i ] - before == 1 ) {
		before = v[ i ];
	  } else {
		ps.push_back( make_pair( start, before ) );
		start = before = v[ i ];
	  }
	}
	ps.push_back( make_pair( start, before ) );

	int maxSize = 0;
	for ( auto p : ps ) {
	  maxSize = max( maxSize, p.second - p.first + 1 );
	}

	if ( hasWhite ) {
	  for ( int i = 0; i < ps.size() - 1; i++ ) {
		if ( ps[ i + 1 ].first - ps[ i ].second == 2 ) {
		  maxSize = max( maxSize, ps[ i + 1 ].second - ps[ i ].first + 1 );
		}
	  }
	}
	cout << maxSize << endl;
  }
  return 0;
}
```