#include <fstream>

using namespace std;

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

int D,n,k;
int v[1000005];
int d[1000005];

void read()
{
    fin >> D >> n >> k;
    for(int i = 1; i <= n; ++i){
        fin >> v[i];
    }
}

void runAlgorithm()
{
    int l = 1, r = 1;
    for(int i = 1; i <= n; ++i){
        d[i] = min(d[i - 1] + 1, d[i - (r - l + 1)] + k);
        ++r;
        while(v[r] > v[l] + D){
            ++l;
        }
    }
    fout << d[n];
}

int main()
{
    read();
    runAlgorithm();
    return 0;
}