#include <iostream>
#include <vector>
#include <algorithm>

int main() {
	int n, k;
	std::vector<int> cards;
	cards.reserve(100000);

	while (std::cin >> n >> k, n + k != 0) {
		bool whiteExist = false;

		for (int i = 0; i < k; ++i) {
			int c;
			std::cin >> c;

			if (c == 0)
				whiteExist = true;
			else
				cards.push_back(c);
		}

		cards.push_back(n + 100);
		std::sort(cards.begin(), cards.end());

		int maxChain = 0;
		int nowChain = 1, prevChain = 0;
		bool canWhiteChain = false;

		for (size_t i = 1; i < cards.size(); ++i) {
			if (cards[i] - cards[i - 1] == 1)
				++nowChain;
			else {
				maxChain = std::max(
					maxChain,
					(canWhiteChain ? nowChain + prevChain + 1 : nowChain)
				);

				canWhiteChain = whiteExist && cards[i] - cards[i - 1] == 2;

				prevChain = nowChain;
				nowChain = 1;
			}
		}

		std::cout << maxChain << std::endl;

		cards.clear();
	}
}
### 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 <iostream>
#include <vector>
#include <algorithm>

int main() {
	int n, k;
	std::vector<int> cards;
	cards.reserve(100000);

	while (std::cin >> n >> k, n + k != 0) {
		bool whiteExist = false;

		for (int i = 0; i < k; ++i) {
			int c;
			std::cin >> c;

			if (c == 0)
				whiteExist = true;
			else
				cards.push_back(c);
		}

		cards.push_back(n + 100);
		std::sort(cards.begin(), cards.end());

		int maxChain = 0;
		int nowChain = 1, prevChain = 0;
		bool canWhiteChain = false;

		for (size_t i = 1; i < cards.size(); ++i) {
			if (cards[i] - cards[i - 1] == 1)
				++nowChain;
			else {
				maxChain = std::max(
					maxChain,
					(canWhiteChain ? nowChain + prevChain + 1 : nowChain)
				);

				canWhiteChain = whiteExist && cards[i] - cards[i - 1] == 2;

				prevChain = nowChain;
				nowChain = 1;
			}
		}

		std::cout << maxChain << std::endl;

		cards.clear();
	}
}
```