#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
using namespace std;
int main(){
	int N,M;
	while(1){
	int n[100001]={};
	bool Q[100001]={};
	int G=0;
	int H=0;
	cin>>N>>M;if(N==0&&M==0)break;
	for(int i=0;i<M;i++)
	{int t;
		cin>>t;Q[t]=true;
	}
	//sort(n,n+M);
	int max=0,h=0,y=0;int w=0,z=-1;
	int D=2;
	if(Q[0]==false)D=1;
	int P=0,PY=1;
	for(int i=1;i<=N;i++)
	{
		if(Q[i]==true){
			h++;
		y++;}
		else{
		P++;PY++;
		if(Q[0]==true){
			if(P!=D)h++;
			if(PY!=D)y++;}
		if(P==D){
			if(max<h)max=h;
			P=0;h=0;
			}
		if(Q[0]==true&&PY==D){
			if(max<y)max=y;
			PY=0;y=0;
		}
		}
	
	}
	if(max<h)max=h;
	if(Q[0]==true&&max<y)max=y;
	if(max==0){
		if(Q[0]==true)max=2;
		else max=1;}

	cout<<max<<endl;
	}
	return 0;
}
### Prompt

In CPP, your task is to solve 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<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
using namespace std;
int main(){
	int N,M;
	while(1){
	int n[100001]={};
	bool Q[100001]={};
	int G=0;
	int H=0;
	cin>>N>>M;if(N==0&&M==0)break;
	for(int i=0;i<M;i++)
	{int t;
		cin>>t;Q[t]=true;
	}
	//sort(n,n+M);
	int max=0,h=0,y=0;int w=0,z=-1;
	int D=2;
	if(Q[0]==false)D=1;
	int P=0,PY=1;
	for(int i=1;i<=N;i++)
	{
		if(Q[i]==true){
			h++;
		y++;}
		else{
		P++;PY++;
		if(Q[0]==true){
			if(P!=D)h++;
			if(PY!=D)y++;}
		if(P==D){
			if(max<h)max=h;
			P=0;h=0;
			}
		if(Q[0]==true&&PY==D){
			if(max<y)max=y;
			PY=0;y=0;
		}
		}
	
	}
	if(max<h)max=h;
	if(Q[0]==true&&max<y)max=y;
	if(max==0){
		if(Q[0]==true)max=2;
		else max=1;}

	cout<<max<<endl;
	}
	return 0;
}
```