#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

int main(){
	while(1){
		int n, k;
		scanf("%d %d", &n, &k);
		if(n == 0 && k == 0) break;
		vector<int> v;
		for(int i=0; i<k; i++){
			int t;
			scanf("%d", &t);
			v.push_back(t);
		}
		sort(v.begin(), v.end());
		int ans = 1;

		if(v[0] != 0){
			int dp[k];
			dp[0] = 1;
			for(int i=1; i<k; i++){
				if(v[i] - v[i-1] == 1) dp[i] = dp[i-1] + 1;
				else dp[i] = 1;
				ans = max(ans, dp[i]);
			}
		}else{
			vector<int> w;
			int dp[k];
			dp[1] = 1;
			for(int i=2; i<k; i++){
				if(v[i] - v[i-1] == 1) dp[i] = dp[i-1] + 1;
				else{
					w.push_back(dp[i-1]);
					dp[i] = 1;
				}
			}
			w.push_back(dp[k-1]);
			for(int i=0; i<w.size()-1; i++){
				ans = max(ans, w[i] + 1 + w[i+1]);
			}
		}
		printf("%d\n", ans);
	}
	return 0;
}
### Prompt

Construct a cpp code solution to the problem outlined:

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 <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

int main(){
	while(1){
		int n, k;
		scanf("%d %d", &n, &k);
		if(n == 0 && k == 0) break;
		vector<int> v;
		for(int i=0; i<k; i++){
			int t;
			scanf("%d", &t);
			v.push_back(t);
		}
		sort(v.begin(), v.end());
		int ans = 1;

		if(v[0] != 0){
			int dp[k];
			dp[0] = 1;
			for(int i=1; i<k; i++){
				if(v[i] - v[i-1] == 1) dp[i] = dp[i-1] + 1;
				else dp[i] = 1;
				ans = max(ans, dp[i]);
			}
		}else{
			vector<int> w;
			int dp[k];
			dp[1] = 1;
			for(int i=2; i<k; i++){
				if(v[i] - v[i-1] == 1) dp[i] = dp[i-1] + 1;
				else{
					w.push_back(dp[i-1]);
					dp[i] = 1;
				}
			}
			w.push_back(dp[k-1]);
			for(int i=0; i<w.size()-1; i++){
				ans = max(ans, w[i] + 1 + w[i+1]);
			}
		}
		printf("%d\n", ans);
	}
	return 0;
}
```