#include <fstream>

using namespace std;

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

int d,n,k,i;
int v[1000001],dp[1000001],sol[1000001];

int main()
{
    fin >> d >> n >> k;
    for (i=1; i<=n; i++)
        fin >> v[i];
    int st = 1;
    for (int dr=1; dr<=n; dr++)
    {
        while (st <= dr && v[dr]-v[st] >= d)
            st++;
        dp[dr] = st;
    }
    for (i=1; i<=n; i++)
        sol[i] = min(sol[i-1]+1, sol[dp[i]-1]+k);
    fout << sol[n];
    return 0;
}