#include <fstream>

using namespace std;

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

const int NMAX=1e6+5;
int n, d, k, v[NMAX], dp[NMAX];

int main()
{
    in>>d>>n>>k;
    int j=1;
    for(int i=1;i<=n;i++)
    {
        in>>v[i];
        while(v[i]-v[j]>=d)
            j++;
        dp[i]=min(dp[i-1]+1, dp[j-1]+k);
    }
    out<<dp[n];
    return 0;
}