#include <fstream>
#include <algorithm>

using namespace std;

#define maxn

int d,n,k,p1;
int v[1000010], dp[1000010];
ifstream fin("zombie.in");
ofstream fout("zombie.out");

int main()
{


    fin>>d>>n>>k;
    p1=1;
    for(int i=1; i<=n; ++i)
    {
        fin>>v[i];
        while(v[i]-v[p1]>=d)
            ++p1;
        dp[i]=min(dp[i-1]+1, dp[p1-1]+k);
    }

    fout<<dp[n];
}