#include <bits/stdc++.h>

using namespace std;
ifstream f("zombie.in");
ofstream g("zombie.out");
int n,d,k,a[1000005];
void Citire()
{
    int i;
    f>>d>>n>>k;
    for(i=1;i<=n;i++)
        f>>a[i];
}
void Rezolvare()
{
    int c=1,distanta=1,i=2,rez=0;
    while(i<=n)
    {
        if(a[i]-a[c]>d && distanta==1)
            {rez++;
            c=i;
            i++;}
        while(a[i]-a[c]<=d)
           {
            distanta++;
            i++;}
        if(a[i]-a[c]>d && distanta>1)
            {
                distanta=1;
                rez=rez+k;
                c=i;
                i++;
            }
        i++;
    }
    g<<rez<<"\n";
}
int main()
{
    Citire();
    Rezolvare();
    return 0;
}