#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <vector>
#include <set>
#include <queue>
#include <string>
#include <utility>
#include <cctype>
#include <algorithm>
#include <iostream>
using namespace std;
typedef pair<int,int> P;
int main() {
	vector<int> v1;
	vector<P> v2;
	int n,k;
	bool f;
	while(scanf("%d %d",&n,&k),n|k) {
		f=0;
		v1.clear();v2.clear();
		for(int i=0;i<k;i++) {
			int x;
			scanf("%d",&x);
			if(x==0) f=1; else v1.push_back(x);
		}
		sort(v1.begin(),v1.end());
		int s=v1[0];
		for(int i=1;i<v1.size();i++) {
			if(v1[i]!=v1[i-1]+1) {
				v2.push_back(P(s,v1[i-1]));
				s=v1[i];
			}
		}
		v2.push_back(P(s,v1[v1.size()-1]));
		int ans=0;
		for(int i=0;i<v2.size();i++) {
			ans=max(ans,v2[i].second-v2[i].first+1);
			if(f) {
				if(v2[i].first>1||v2[i].second<n) ans=max(ans,(v2[i].second-v2[i].first+1)+1);
				if(i<v2.size()-1) {
					if(v2[i].second+2==v2[i+1].first) ans=max(ans,(v2[i].second-v2[i].first+1)+(v2[i+1].second-v2[i+1].first+1)+1);
				}
			}
		}
		printf("%d\n",ans);
	}
}
### 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 <cstdio>
#include <cstdlib>
#include <cstring>
#include <vector>
#include <set>
#include <queue>
#include <string>
#include <utility>
#include <cctype>
#include <algorithm>
#include <iostream>
using namespace std;
typedef pair<int,int> P;
int main() {
	vector<int> v1;
	vector<P> v2;
	int n,k;
	bool f;
	while(scanf("%d %d",&n,&k),n|k) {
		f=0;
		v1.clear();v2.clear();
		for(int i=0;i<k;i++) {
			int x;
			scanf("%d",&x);
			if(x==0) f=1; else v1.push_back(x);
		}
		sort(v1.begin(),v1.end());
		int s=v1[0];
		for(int i=1;i<v1.size();i++) {
			if(v1[i]!=v1[i-1]+1) {
				v2.push_back(P(s,v1[i-1]));
				s=v1[i];
			}
		}
		v2.push_back(P(s,v1[v1.size()-1]));
		int ans=0;
		for(int i=0;i<v2.size();i++) {
			ans=max(ans,v2[i].second-v2[i].first+1);
			if(f) {
				if(v2[i].first>1||v2[i].second<n) ans=max(ans,(v2[i].second-v2[i].first+1)+1);
				if(i<v2.size()-1) {
					if(v2[i].second+2==v2[i+1].first) ans=max(ans,(v2[i].second-v2[i].first+1)+(v2[i+1].second-v2[i+1].first+1)+1);
				}
			}
		}
		printf("%d\n",ans);
	}
}
```