#include <bits/stdc++.h>

using namespace std;

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

int d,n,k,st;
int v[1000005];
long long sol[1000005];

int main()
{
f>>d>>n>>k;
for(int i=1;i<=n;i++)
 f>>v[i];
st=0;
///rezolvare
sol[1]=1;
for(int i=2;i<=n;i++){
  while(v[i]-v[st]>=d) st++;
  sol[i]=min(sol[i-1]+1,sol[st-1]+k);
}
g<<sol[n];
}