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

#define repi(i,a,b) for(int i=(a);i<(b);i++)
#define rep(i,n) for(int i=0;i<(n);i++)

bool c[100001];
int n, k;

int main() {
	ios::sync_with_stdio(false);
	
	while(1) {
		cin >> n >> k;
		if(!(n|k))break;
		rep(i, n+1)c[i]=false;
		int t;
		rep(i, k) {
			cin >> t;
			c[t] = true;
		}
		int l=0;
		if(c[0]) {
			int j=0, t=0;
			repi(i, 1, n+1) {
				if(!c[i])continue;
				j=i;
				while(j<=n && c[j])j++;
				t=j;
				j++;
				while(j<=n && c[j])j++;
				l = max(l, j-i);
				i=t;
			}
		}else {
			int j=0;
			repi(i, 1, n+1) {
				if(!c[i])continue;
				j=i;
				while(j<=n && c[j])j++;
				l = max(l, j-i);
				i=j;
			}
		}
		cout <<l <<endl;
	}
	
	return 0;
}
### Prompt

Your challenge is to write a cpp solution to 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 <algorithm>
#include <cstring>
using namespace std;

#define repi(i,a,b) for(int i=(a);i<(b);i++)
#define rep(i,n) for(int i=0;i<(n);i++)

bool c[100001];
int n, k;

int main() {
	ios::sync_with_stdio(false);
	
	while(1) {
		cin >> n >> k;
		if(!(n|k))break;
		rep(i, n+1)c[i]=false;
		int t;
		rep(i, k) {
			cin >> t;
			c[t] = true;
		}
		int l=0;
		if(c[0]) {
			int j=0, t=0;
			repi(i, 1, n+1) {
				if(!c[i])continue;
				j=i;
				while(j<=n && c[j])j++;
				t=j;
				j++;
				while(j<=n && c[j])j++;
				l = max(l, j-i);
				i=t;
			}
		}else {
			int j=0;
			repi(i, 1, n+1) {
				if(!c[i])continue;
				j=i;
				while(j<=n && c[j])j++;
				l = max(l, j-i);
				i=j;
			}
		}
		cout <<l <<endl;
	}
	
	return 0;
}
```