#include<fstream>
#include<algorithm>
using namespace std;
unsigned int d,n,k,m,i,j,a[1000001],b[1000001];
int main()
{
	ifstream f("zombie.in");
	ofstream g("zombie.out");
	f>>d>>n>>k;
	for(i=1;i<=n;++i)
		f>>a[i];
	b[n]=1;
	i=n;
	while(--i)
	{
		m=i+1;
		while(a[m]-a[i]<d&&m<n&&m-i<=d)
			++m;
		b[i]=min(b[i+1]+1,b[m+1]+k);
	}
	g<<b[1];
	return 0;
}