#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
bool iscard[1000001];
int dp[2][1000001];
int main(){
        int n,m;
        while(scanf("%d%d",&n,&m),(n|m)){
                memset(dp,0,sizeof(dp));
                memset(iscard,0,sizeof(iscard));
                for(int i = 0; i < m; i++){
                        int tmp;
                        scanf("%d",&tmp);
                        iscard[tmp] = true;
                }
                bool zero = iscard[0];
                int ans = -10000;
                for(int i = 1; i < n+1; i++){
                        if(iscard[i]){
                                dp[0][i] = dp[0][i-1] + 1;
                                dp[1][i] = dp[1][i-1] + 1;
                        }
                        else if(zero){
                                dp[1][i] = dp[0][i-1] + 1;
                        }
                        ans = max(ans,max(dp[0][i],dp[1][i]));
                }
                printf("%d\n",ans);
        }
        return 0;
}
### 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<algorithm>
#include<cstring>
using namespace std;
bool iscard[1000001];
int dp[2][1000001];
int main(){
        int n,m;
        while(scanf("%d%d",&n,&m),(n|m)){
                memset(dp,0,sizeof(dp));
                memset(iscard,0,sizeof(iscard));
                for(int i = 0; i < m; i++){
                        int tmp;
                        scanf("%d",&tmp);
                        iscard[tmp] = true;
                }
                bool zero = iscard[0];
                int ans = -10000;
                for(int i = 1; i < n+1; i++){
                        if(iscard[i]){
                                dp[0][i] = dp[0][i-1] + 1;
                                dp[1][i] = dp[1][i-1] + 1;
                        }
                        else if(zero){
                                dp[1][i] = dp[0][i-1] + 1;
                        }
                        ans = max(ans,max(dp[0][i],dp[1][i]));
                }
                printf("%d\n",ans);
        }
        return 0;
}
```