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

int main(){
	int n,k;
	int num[100000];
	while(1){
		cin >> n >> k;
		if(!n && !k) break;
		bool flag = false;
		for(int i = 0;i < k;i++) {
			cin >> num[i];
			if(num[i] == 0) flag = true;
		}
		sort(num,num + k);
		int ma = -1,prev,cnt = 1;
		if(!flag){
			prev = num[0];
			for(int i = 1;i < k;i++){
				if(num[i] - prev == 1) {
					cnt++;
					ma = max(ma,cnt);
				}
				else cnt = 1;
				prev = num[i];
			}
		}
		else{
			int pcnt = -1;
			prev = num[1];
			for(int i = 2;i < k;i++){
				if(num[i] - prev == 1){
					cnt++;
					ma = max(cnt + pcnt + 1,ma);
				}
				else if(num[i] - prev == 2){
					pcnt = cnt;
					cnt = 1;
					ma = max(ma,cnt + pcnt + 1);
				}
				else{
					pcnt = -1;
					cnt = 1;
				}
				prev = num[i];
			}
		}
		cout << ma << 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 <algorithm>
using namespace std;

int main(){
	int n,k;
	int num[100000];
	while(1){
		cin >> n >> k;
		if(!n && !k) break;
		bool flag = false;
		for(int i = 0;i < k;i++) {
			cin >> num[i];
			if(num[i] == 0) flag = true;
		}
		sort(num,num + k);
		int ma = -1,prev,cnt = 1;
		if(!flag){
			prev = num[0];
			for(int i = 1;i < k;i++){
				if(num[i] - prev == 1) {
					cnt++;
					ma = max(ma,cnt);
				}
				else cnt = 1;
				prev = num[i];
			}
		}
		else{
			int pcnt = -1;
			prev = num[1];
			for(int i = 2;i < k;i++){
				if(num[i] - prev == 1){
					cnt++;
					ma = max(cnt + pcnt + 1,ma);
				}
				else if(num[i] - prev == 2){
					pcnt = cnt;
					cnt = 1;
					ma = max(ma,cnt + pcnt + 1);
				}
				else{
					pcnt = -1;
					cnt = 1;
				}
				prev = num[i];
			}
		}
		cout << ma << endl;
	}
	return 0;	
}
```