#include<cstdio>
#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<sstream>

using namespace std;

#define reps(i,f,n) for(int i=f;i<int(n);i++)
#define rep(i,n) reps(i,0,n)

int here[100001];
int dp1[100001];
int dp2[100001];

int main(){
	while(1){
		int n,m;
		cin>>n>>m;
		if(n==0)break;
		
		rep(i,100001)here[i]=dp1[i]=dp2[i]=0;
		
		bool dpflg = false;
		
		rep(i,m){
			int a;
			cin>>a;
			if(a==0) dpflg=true;
			
			here[a]=1;
		}
		
		int maxi1 = 0;
		int maxi2 = 0;
		
		reps(i,1,n+1){
			if(here[i]==1)dp1[i] = dp1[i-1]+1;
			maxi1 = max(dp1[i], maxi1);
		}
		
		reps(i,1,n+1){
			if(here[i]==1)dp2[i] = dp2[i-1]+1;
			else dp2[i] = dp1[i-1]+1;
			maxi2 = max(dp2[i], maxi2);
		}
		
		if(!dpflg){
			printf("%d\n",maxi1);
		}else{
			printf("%d\n",maxi2);
		}
	}
}
### 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<cstdio>
#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<sstream>

using namespace std;

#define reps(i,f,n) for(int i=f;i<int(n);i++)
#define rep(i,n) reps(i,0,n)

int here[100001];
int dp1[100001];
int dp2[100001];

int main(){
	while(1){
		int n,m;
		cin>>n>>m;
		if(n==0)break;
		
		rep(i,100001)here[i]=dp1[i]=dp2[i]=0;
		
		bool dpflg = false;
		
		rep(i,m){
			int a;
			cin>>a;
			if(a==0) dpflg=true;
			
			here[a]=1;
		}
		
		int maxi1 = 0;
		int maxi2 = 0;
		
		reps(i,1,n+1){
			if(here[i]==1)dp1[i] = dp1[i-1]+1;
			maxi1 = max(dp1[i], maxi1);
		}
		
		reps(i,1,n+1){
			if(here[i]==1)dp2[i] = dp2[i-1]+1;
			else dp2[i] = dp1[i-1]+1;
			maxi2 = max(dp2[i], maxi2);
		}
		
		if(!dpflg){
			printf("%d\n",maxi1);
		}else{
			printf("%d\n",maxi2);
		}
	}
}
```