#include <bits/stdc++.h>

#define ALL(a) (a).begin(), (a).end()

using namespace std;

signed main(){
	while(true) {
		int n; cin >> n;
		if(n == 0) break;
		int k; cin >> k;
		vector<int> arr(k);
		for(auto &&e : arr) cin >> e;
		sort(ALL(arr));
		int ans = 0;
		if(arr[0] == 0) {
			int acc = 1;
			int prev = 0;
			for(size_t i = 2; i < k; i++) {
				switch(arr[i] - arr[i-1]) {
					case 1:
						acc += 1;
						break;
					case 2:
						ans = max(ans, acc + prev + 1);
						prev = acc;
						acc = 1;
						break;
					default:
						ans = max(ans, acc + prev + 1);
						acc = 1;
						prev = 0;
						break;
				}
			}
			ans = max(ans, acc + prev + 1);
		} else {
			int acc = 1;
			for(size_t i = 1; i < k; i++) {
				if(arr[i] - arr[i-1] == 1) {
					acc += 1;
				} else {
					ans = max(ans, acc);
					acc = 1;
				}
			}
			ans = max(ans, acc);
		}
		cout << ans << "\n";
	}
	return 0;
}



### Prompt

Create a solution in CPP for 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 <bits/stdc++.h>

#define ALL(a) (a).begin(), (a).end()

using namespace std;

signed main(){
	while(true) {
		int n; cin >> n;
		if(n == 0) break;
		int k; cin >> k;
		vector<int> arr(k);
		for(auto &&e : arr) cin >> e;
		sort(ALL(arr));
		int ans = 0;
		if(arr[0] == 0) {
			int acc = 1;
			int prev = 0;
			for(size_t i = 2; i < k; i++) {
				switch(arr[i] - arr[i-1]) {
					case 1:
						acc += 1;
						break;
					case 2:
						ans = max(ans, acc + prev + 1);
						prev = acc;
						acc = 1;
						break;
					default:
						ans = max(ans, acc + prev + 1);
						acc = 1;
						prev = 0;
						break;
				}
			}
			ans = max(ans, acc + prev + 1);
		} else {
			int acc = 1;
			for(size_t i = 1; i < k; i++) {
				if(arr[i] - arr[i-1] == 1) {
					acc += 1;
				} else {
					ans = max(ans, acc);
					acc = 1;
				}
			}
			ans = max(ans, acc);
		}
		cout << ans << "\n";
	}
	return 0;
}



```