#include <fstream>
#include <algorithm>

using namespace std;

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

const int MAX_N = 1000000;

int T[MAX_N + 5];
int C[MAX_N + 5];

int main() {
    int i, j, n, d, k;

    in >> d >> n >> k;
    for(i = 1; i <= n; i++) in >> T[i];
    for(i = 1, j = 1; i <= n; i++) {
        while(T[j] + d < T[i]) j++;
        C[i] = min(C[i-1] + 1, C[j-1] + k);
    }

    out << C[n];
    return 0;
}