#include <fstream>
using namespace std;
 
const int N=1000005;
int v[N],a[N],d[N],n,k,D;
 
ifstream in("zombie.in");
ofstream out("zombie.out");
 
inline int min(int a,int b)
{
return a<b ? a : b;
}
 
int main()
{
int i,j;
in>>D>>n>>k;
for (i=1;i<=n;i++)
in>>d[i];
for (i=j=1;i<=n;i++)
{
for(;j<=n && d[j]-d[i]<=D;j++);
a[i]=j-1;
}
v[n]=1;
for (i=n-1;i;i--)
v[i]=min(v[i+1]+1,v[a[i]+1]+k);
out<<v[1]<<"\n";
return 0;
}