#include <iostream>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

int main() {
	
	while(true){
	int n,k;
	cin >> n >> k;
	if(n==0&&k==0)break;

	vector<int> s;
	s.reserve(n+1);
	bool sp=false;
	for(int i=0;i<k;i++){
		int t;
		cin >> t;
		if(t==0) sp=true;
		else s.push_back(t);
	}
	s.push_back(n+100);
	sort(s.begin(),s.end());

	vector<pair<int,int>> pairs;	
	int prev=-10;
	pair<int,int> pair_;

	int ans =0;
	for( int i=0;i<s.size();i++){
		if( s[i]==prev+1){
			pair_.second=s[i];
		}else{
			if(i!=0){
//				cout << pair_.first << "-" << pair_.second << endl;
				pairs.push_back(pair_);
				ans = max(ans, pair_.second-pair_.first+1);
			}
			pair_.first=pair_.second=s[i];
		}
		prev = s[i];
	}
	if( sp&& k<n){
		ans+1;
	}

	if( sp ){
		for(int i=0;i<pairs.size()-1;i++){
			auto &p0=pairs[i];
			auto &p1=pairs[i+1];
			if( p0.second + 2 == p1.first){
				ans = max(ans, p0.second-p0.first+p1.second-p1.first+3);
			}
		}
	}
	cout << ans << endl;
	}

	return 0;
}
### 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 <iostream>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

int main() {
	
	while(true){
	int n,k;
	cin >> n >> k;
	if(n==0&&k==0)break;

	vector<int> s;
	s.reserve(n+1);
	bool sp=false;
	for(int i=0;i<k;i++){
		int t;
		cin >> t;
		if(t==0) sp=true;
		else s.push_back(t);
	}
	s.push_back(n+100);
	sort(s.begin(),s.end());

	vector<pair<int,int>> pairs;	
	int prev=-10;
	pair<int,int> pair_;

	int ans =0;
	for( int i=0;i<s.size();i++){
		if( s[i]==prev+1){
			pair_.second=s[i];
		}else{
			if(i!=0){
//				cout << pair_.first << "-" << pair_.second << endl;
				pairs.push_back(pair_);
				ans = max(ans, pair_.second-pair_.first+1);
			}
			pair_.first=pair_.second=s[i];
		}
		prev = s[i];
	}
	if( sp&& k<n){
		ans+1;
	}

	if( sp ){
		for(int i=0;i<pairs.size()-1;i++){
			auto &p0=pairs[i];
			auto &p1=pairs[i+1];
			if( p0.second + 2 == p1.first){
				ans = max(ans, p0.second-p0.first+p1.second-p1.first+3);
			}
		}
	}
	cout << ans << endl;
	}

	return 0;
}
```