#include <iostream>
#include <fstream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <vector>
using namespace std;
#define maxn 1000010

int D, N, K;
int T[maxn], Din[maxn];

int main() {
    fstream f1, f2;
    f1.open("zombie.in", ios::in);
    f2.open("zombie.out", ios::out);
    int i, j, p, q;

    f1 >> D >> N >> K;
    for(i=1; i<=N; i++) {
         f1 >> T[i];
    }

    int p1 = N, p2 = N;

    for(i=N; i>=1; i--) {
         int lim1 = T[i];
         int lim2 = T[i] + D - 1;
         int nrm = 0;

         p1 = i;
         while(T[p2] > lim2) p2 --;

         Din[i] = min(1 + Din[i+1], K + Din[p2 + 1]);
    }

    f2 << Din[1];

    f1.close(); f2.close();
    return 0;
}