#include <fstream>

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