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

const int N = 100000;
int step[N + 1];
bool a[N + 1];

int main(){
	int n, k, buf, mlen = 0;
	bool iszero;
	while(cin >> n >> k, n && k){
		fill(step, step + (N + 1), 0);
		fill(a, a + (N + 1), false);
		iszero = false;
		for(int i = 0;i < k;++i){
			cin >> buf;
			if(buf == 0) iszero = true;
			else a[buf] = true;
		}
		for(int i = 1;i <= n;++i){
			if(a[i]) step[i] = step[i - 1] + 1;
		}
		for(int i = 1;i <= n;++i){
			mlen = max(mlen, step[i]);
		}
		if(iszero){
			queue<int> q;
			for(int i = n - 1;0 < i;--i){
				if(a[i + 1] && a[i]) step[i] = step[i + 1];
			}
			for(int i = 2;i < n;++i){
				if(a[i - 1] && a[i + 1] && !a[i]) q.push(i);
			}
			while(!q.empty()){
				int idx = q.front();
				q.pop();
				mlen = max(mlen, step[idx - 1] + step[idx + 1] + 1);
			}
		}
		cout << mlen << endl;
	}
	return 0;
}
### Prompt

Please create a solution in CPP 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 <queue>
using namespace std;

const int N = 100000;
int step[N + 1];
bool a[N + 1];

int main(){
	int n, k, buf, mlen = 0;
	bool iszero;
	while(cin >> n >> k, n && k){
		fill(step, step + (N + 1), 0);
		fill(a, a + (N + 1), false);
		iszero = false;
		for(int i = 0;i < k;++i){
			cin >> buf;
			if(buf == 0) iszero = true;
			else a[buf] = true;
		}
		for(int i = 1;i <= n;++i){
			if(a[i]) step[i] = step[i - 1] + 1;
		}
		for(int i = 1;i <= n;++i){
			mlen = max(mlen, step[i]);
		}
		if(iszero){
			queue<int> q;
			for(int i = n - 1;0 < i;--i){
				if(a[i + 1] && a[i]) step[i] = step[i + 1];
			}
			for(int i = 2;i < n;++i){
				if(a[i - 1] && a[i + 1] && !a[i]) q.push(i);
			}
			while(!q.empty()){
				int idx = q.front();
				q.pop();
				mlen = max(mlen, step[idx - 1] + step[idx + 1] + 1);
			}
		}
		cout << mlen << endl;
	}
	return 0;
}
```