#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;
int dp[1000001],v[1000001];
int main()
{
    ifstream cin ("zombie.in");
    ofstream cout ("zombie.out");
    int d,n,k;
    cin>>d>>n>>k;
    for(int i=1;i<=n;i++)
    {
        cin>>v[i];
    }
    int j=0;
    for(int i=1;i<=n;i++)
    {
       while(v[i]-v[j]>=d)
       {
           j++;
       }
        dp[i]=min(dp[i-1]+1,k+dp[j-1]);
    }
    cout<<dp[n];
    return 0;
}