#include<iostream>
#include<fstream>
int a[1000001],b[1000001],c[1000001];
using namespace std;
int main(void)
{
	int i,d,n,k,poz;
	fstream f,g;
	f.open("zombie.in",ios::in);
	g.open("zombie.out",ios::out);
	f>>d>>n>>k;
	for (i=1;i<=n;i++)
		f>>a[i];
	
	poz=1;
	b[1]=0;
	for (i=2;i<=n;i++)
	{
		while (a[i]-a[poz]>=d)
			poz++;
		b[i]=poz-1;
	}
	for (i=1;i<=n;i++)
		c[i]=min(1+c[i-1],k+c[b[i]]);
	g<<c[n];
}