#include <iostream>
#include <fstream>

using namespace std;

ifstream in("zombie.in");
ofstream out("zombie.out");

const int dim = 1000005;

int n,d,k,timp[dim];
int q[dim],st,dr,consum[dim],cons;

int main()
{
    in >> d >> n >> k;
    for (int i=1; i<=n; i++)
    {
        in >> timp[i];
    }
    int cate;
    st = 0;
    dr = -1;

    for (int i=1; i<=n; i++)
    {
        if (timp[i] - q[st] + 1 >= d)
        {
            cate = 0;
            while (st <= dr && timp[i] - q[st] + 1 >= d)
            {
                st++;
                cate++;
            }
        }
        q[++dr] = timp[i];
        consum[i] = min(consum[i-1] + 1 , consum[st] + k);
    }
    out << consum[n];
    return 0;
}