#include <fstream>
using namespace std;

int D,N,K;
int t[1000001];
int d[1000001];

int main()
{
    ifstream fin("zombie.in");
    ofstream fout("zombie.out");

    fin >> D >> N >> K;

    for (int i = 1; i <= N; i++)
        fin >> t[i];

    int cz = 1;
    for (int i = 1; i <= N; i++)
    {
        while (cz < i && t[i] - t[cz] >= D) ++cz;
        d[i] = min(d[i-1]+1,d[cz-1]+K);
    }

    fout << d[N];
}