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

unsigned long i,j,n,d,k,a[1000001],nr,b[1000002],pm;
int main()
{
	FILE *f=fopen("zombie.in","r");
	FILE *g=fopen("zombie.out","w");
	fscanf(f,"%ld%ld%ld",&d,&n,&k);
	for(i=1;i<=n;++i)
		fscanf(f,"%ld",&a[i]);
	b[n]=1;
	b[n+1]=0;
	pm=n;
	for(i=n-1;i>=1;--i)
	{
		nr=1;
		j=i+1;
		while(a[pm]-a[i]>=d&&pm>i)
			--pm;
		b[i]=min(1+b[i+1],b[pm+1]+k);
	}
	fprintf(g,"%ld ",b[1]);
	return 0;
}