#include <fstream>
#include <algorithm>

using namespace std;

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

#define MAX_N 1000010

int d, n, k, p;

int c[MAX_N], A[MAX_N];

int main() {

    f >> d >> n >> k;

    for (int i = 1; i <= n; i++) {
        f >> A[i];

        c[i] = c[i - 1] + 1;

        if (i == 1)
            p = 0;
        else
            while (A[i] - A[p + 1] > d)
                p++;

        c[i] = min(c[i], c[p] + k);
    }

    g << c[n] << "\n";

    return 0;
}