#include <cstdio>
#include <algorithm>
#define MAX 1000010
using namespace std;
int sol[MAX],mom[MAX],n,d,k,i,j;
int main()
{
    freopen("zombie.in","r",stdin);
    freopen("zombie.out","w",stdout);
    scanf("%d%d%d",&d,&n,&k);
    for(i=1;i<=n;++i)scanf("%d",mom+i);
    for(i=1,j=1;i<=n;++i){
        while(mom[j]<=mom[i]-d)++j;
        sol[i]=min(sol[i-1]+1,sol[j-1]+k);
    }
    printf("%d\n",sol[n]);
    return 0;
}