#include <bits/stdc++.h>
#define FOR(I,X,Y) for(long int I=X;I<Y;I++)
#define REP(I,X) for(long int I=X;I>=0;I--)
#define INF 1e9+7
using namespace std;

int main(){
  int n,k,q;
  vector<int> ans;
  while(1){
    cin >> n >> k;
    if(n == 0 && k == 0)break;
    vector<bool> given(n+2,0);
    vector<int> left(n+2,0);
    vector<int> right(n+2,0);
    FOR(i,0,k){
      cin >> q;
      given[q] = 1;
    }
    if(given[0]){
      given[0] = 0;
      FOR(i,1,n+1)if(given[i])left[i] = left[i-1] + 1;
      REP(i,n)if(given[i] && i)right[i] = right[i+1] + 1;
      int ma = 0;
      FOR(i,1,n+1)ma = max(ma,left[i-1]+right[i+1]+1);
      ans.push_back(ma);
    }
    else{
      FOR(i,1,n+1)if(given[i])left[i] = left[i-1] + 1;
      int ma = 0;
      FOR(i,1,n+1)ma = max(ma,left[i]);
      ans.push_back(ma);
    }
  }
  for(auto x:ans)cout << x << endl;
}


### Prompt

Please formulate 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 <bits/stdc++.h>
#define FOR(I,X,Y) for(long int I=X;I<Y;I++)
#define REP(I,X) for(long int I=X;I>=0;I--)
#define INF 1e9+7
using namespace std;

int main(){
  int n,k,q;
  vector<int> ans;
  while(1){
    cin >> n >> k;
    if(n == 0 && k == 0)break;
    vector<bool> given(n+2,0);
    vector<int> left(n+2,0);
    vector<int> right(n+2,0);
    FOR(i,0,k){
      cin >> q;
      given[q] = 1;
    }
    if(given[0]){
      given[0] = 0;
      FOR(i,1,n+1)if(given[i])left[i] = left[i-1] + 1;
      REP(i,n)if(given[i] && i)right[i] = right[i+1] + 1;
      int ma = 0;
      FOR(i,1,n+1)ma = max(ma,left[i-1]+right[i+1]+1);
      ans.push_back(ma);
    }
    else{
      FOR(i,1,n+1)if(given[i])left[i] = left[i-1] + 1;
      int ma = 0;
      FOR(i,1,n+1)ma = max(ma,left[i]);
      ans.push_back(ma);
    }
  }
  for(auto x:ans)cout << x << endl;
}


```