#include<iostream>

 #include<cstdio>

 #include<queue>

 #include<cstring>

 #include<algorithm>

 #include<cmath>

 #include<set>

 #define INF 0x3f3f3f3f

 typedef long long ll;

 using namespace std;

 int R, n, a[];

 int main()

 {

     while(cin >> R >> n){

         if(R == -&&n == -) break;

         for(int i = ; i < n; i++){

             cin >> a[i];

         }

         sort(a, a+n);

         int flag=;

         int st = , ans=;//st表示第一个未被覆盖的点

         for(int i = ; i < n;){//一开始这里写的i=0，WA了

             while(i < n&&a[i]-a[st]<=R){

                 i++;

             }

             int t = i-;//此处放一个

             ans++;

             while(i < n&&a[i]-a[t]<=R){

                 i++;

             }

             st = i;

         }

         cout << ans << endl;

     }

     return ;

 }