#include<stdio.h>
#include<string>
#include<stdlib.h>
#include<math.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<numeric>
#include<string.h>

using namespace std;

typedef pair<int,int> pii;

#define rep(i,j) for(int i=0;i<(j);i++)
#define reps(i,j,k) for(int i=j;i<=k;i++)


int main(){
	int n,k,t,ans,cnt;
	for(;;){
		scanf("%d%d",&n,&k);
		if(n==0 && k==0)break;
		vector<int> v,u;
		ans=0;
		rep(i,k){
			scanf("%d",&t);
			v.push_back(t);
		}
		sort(v.begin(),v.end());
		cnt=1;
		if(v[0]==0){
			int f=0;
			rep(i,k-2){
				if(v[i+2]-v[i+1]==1)cnt++;
				else{
					u.push_back(cnt);
					if(v[i+2]-v[i+1]==2)u.push_back(0);
					cnt=1;
				}
			}
			u.push_back(cnt);
			rep(i,u.size()){
				ans=max(ans,u[i]+1);
				if(u[i]==0 && i>0 && i< u.size()-1)ans=max(ans,u[i-1]+u[i+1]+1);
			}
		}else{
			rep(i,k-1){
				if(v[i+1]-v[i]==1)cnt++;
				else {
					ans=max(ans,cnt);
					cnt=1;
				}
			}
			ans=max(ans,cnt);
		}
		printf("%d\n",ans);
	}
	return 0;
}
### Prompt

Develop a solution in CPP to the problem described below:

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<stdio.h>
#include<string>
#include<stdlib.h>
#include<math.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<numeric>
#include<string.h>

using namespace std;

typedef pair<int,int> pii;

#define rep(i,j) for(int i=0;i<(j);i++)
#define reps(i,j,k) for(int i=j;i<=k;i++)


int main(){
	int n,k,t,ans,cnt;
	for(;;){
		scanf("%d%d",&n,&k);
		if(n==0 && k==0)break;
		vector<int> v,u;
		ans=0;
		rep(i,k){
			scanf("%d",&t);
			v.push_back(t);
		}
		sort(v.begin(),v.end());
		cnt=1;
		if(v[0]==0){
			int f=0;
			rep(i,k-2){
				if(v[i+2]-v[i+1]==1)cnt++;
				else{
					u.push_back(cnt);
					if(v[i+2]-v[i+1]==2)u.push_back(0);
					cnt=1;
				}
			}
			u.push_back(cnt);
			rep(i,u.size()){
				ans=max(ans,u[i]+1);
				if(u[i]==0 && i>0 && i< u.size()-1)ans=max(ans,u[i-1]+u[i+1]+1);
			}
		}else{
			rep(i,k-1){
				if(v[i+1]-v[i]==1)cnt++;
				else {
					ans=max(ans,cnt);
					cnt=1;
				}
			}
			ans=max(ans,cnt);
		}
		printf("%d\n",ans);
	}
	return 0;
}
```