#include<fstream>
#include<algorithm>
using namespace std;

unsigned long i,j,n,m,d,k,a[1000001],b[1000002];
int main()
{
	freopen("zombie.in","r",stdin);
	freopen("zombie.out","w",stdout);
	scanf("%ld%ld%ld",&d,&n,&k);
	for(i=1;i<=n;++i)
		scanf("%ld",&a[i]);
	b[n]=1;
	b[n+1]=0;
	m=n;
	i=n-1;
	while(i)
	{
		i--;
		while(a[m]-a[i]>=d&&m>i)
			--m;
		b[i]=min(1+b[i+1],b[m+1]+k);
	}
	printf("%ld ",b[1]);
	return 0;
}