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

using namespace std;

bool a[200000];

int main(){
	int n, k;
	while(true){
		cin >> n >> k;
		if(n == 0 && k == 0){
			break;
		}
		
		for(int i = 0; i <= n; i++){
			a[i] = false;
		}
		
		int num_;
		
		for(int i = 0; i < k; i++){
			cin >> num_;
			a[num_] = true;
		}
		
		int max = 0;
		
		int first, second;
		
		
		if(a[0]){
			first = 0;
			second = 0;
			max = 1;
			for(int i = 1; i <= n; i++){
				if(!a[i]){
					if(i - first - 1 > max){
						max = i - first - 1;
					}
					first = second;
					second = i;
				}
			}
			if(n - first > max){
				max = n - first;
			}
		}else{
			first = 0;
			max = 0;
			for(int i = 1; i <= n; i++){
				if(!a[i]){
					if(i - first - 1 > max){
						max = i - first - 1;
					}
					first = i;
				}
			}
			if(n - first > max){
				max = n - first;
			}
		}
		
		printf("%d\n", max);
	}
	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>
#include <cmath>

using namespace std;

bool a[200000];

int main(){
	int n, k;
	while(true){
		cin >> n >> k;
		if(n == 0 && k == 0){
			break;
		}
		
		for(int i = 0; i <= n; i++){
			a[i] = false;
		}
		
		int num_;
		
		for(int i = 0; i < k; i++){
			cin >> num_;
			a[num_] = true;
		}
		
		int max = 0;
		
		int first, second;
		
		
		if(a[0]){
			first = 0;
			second = 0;
			max = 1;
			for(int i = 1; i <= n; i++){
				if(!a[i]){
					if(i - first - 1 > max){
						max = i - first - 1;
					}
					first = second;
					second = i;
				}
			}
			if(n - first > max){
				max = n - first;
			}
		}else{
			first = 0;
			max = 0;
			for(int i = 1; i <= n; i++){
				if(!a[i]){
					if(i - first - 1 > max){
						max = i - first - 1;
					}
					first = i;
				}
			}
			if(n - first > max){
				max = n - first;
			}
		}
		
		printf("%d\n", max);
	}
	return 0;
}
```