#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;
int crd[100010];
bool num[100010];
int main(){
	int N,K,ctr,cfa;//N?????§K?????°
	vector<int> vt,vf,vt2;
	while(1){
		cin>>N>>K;
		if(N==0&&K==0) break;
		for(int i=0;i<=N;i++){
			num[i]=false;
		}
		for(int i=0;i<K;i++){
			cin>>crd[i];
			num[crd[i]]=true;
		}
		ctr=cfa=0;
		for(int i=1;i<=N;i++){
			if(num[i]){
				if(cfa!=0){vf.push_back(cfa);
				cfa=0;}
				ctr++;
			}
			else{
				if(ctr!=0){vt.push_back(ctr);
				ctr=0;}
				cfa++;
			}
		}

		if(!num[0]){//????´????????????¨???
			sort(vt.begin(),vt.end(),greater<int>());
			cout<<vt[0]<<endl;
		}
		else{//????´????????????¨???
			for(int i=0;i<vt.size()-1;i++){
				if(vf[i]==1){
					vt2.push_back(vt[i]+vt[i+1]+1);
				}
				else{
					vt2.push_back(vt[i]+1);
				}
			}
			sort(vt2.begin(),vt2.end(),greater<int>());
			cout<<vt2[0]<<endl;
		}
	}
	return 0;
}
### 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 <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;
int crd[100010];
bool num[100010];
int main(){
	int N,K,ctr,cfa;//N?????§K?????°
	vector<int> vt,vf,vt2;
	while(1){
		cin>>N>>K;
		if(N==0&&K==0) break;
		for(int i=0;i<=N;i++){
			num[i]=false;
		}
		for(int i=0;i<K;i++){
			cin>>crd[i];
			num[crd[i]]=true;
		}
		ctr=cfa=0;
		for(int i=1;i<=N;i++){
			if(num[i]){
				if(cfa!=0){vf.push_back(cfa);
				cfa=0;}
				ctr++;
			}
			else{
				if(ctr!=0){vt.push_back(ctr);
				ctr=0;}
				cfa++;
			}
		}

		if(!num[0]){//????´????????????¨???
			sort(vt.begin(),vt.end(),greater<int>());
			cout<<vt[0]<<endl;
		}
		else{//????´????????????¨???
			for(int i=0;i<vt.size()-1;i++){
				if(vf[i]==1){
					vt2.push_back(vt[i]+vt[i+1]+1);
				}
				else{
					vt2.push_back(vt[i]+1);
				}
			}
			sort(vt2.begin(),vt2.end(),greater<int>());
			cout<<vt2[0]<<endl;
		}
	}
	return 0;
}
```