#include <fstream>
#include <deque>
#include <algorithm>
using namespace std;

#define NMax 1000005

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

int d,n,k;
int v[NMax],D[NMax];
deque<int> dq;

int main()
{
    int i,ls;
    f>>d>>n>>k;

    for(i=1;i<=n;i++) f>>v[i];

    for(i=1;i<=n;i++)
    {
        dq.push_back(i);
        while(v[i]-v[dq.front()]>=d) dq.pop_front();
        D[i]=min(D[i-1]+1,D[dq.front()-1]+k);
    }

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

    f.close();
    g.close();
    return 0;
}