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

unsigned int i,j,n,d,k,a[100002],nr,b[100002];
int main()
{
	FILE *f=fopen("zombie.in","r");
	FILE *g=fopen("zombie.out","w");
	fscanf(f,"%d%d%d",&d,&n,&k);
	for(i=1;i<=n;++i)
		fscanf(f,"%d",&a[i]);
	b[n]=1;
	b[n+1]=0;
	for(i=n-1;i>=1;--i)
	{
		nr=1;
		j=i+1;
		while(a[j]-a[i]<d&&nr<=d&&j<=d)
			++nr,++j;
		b[i]=min(1+b[i+1],b[j]+k);
	}
	fprintf(g,"%d ",b[1]);
	return 0;
}