#include <iostream>
#include <vector>
using namespace std;
typedef long long ll;
int main(){
  ll n,d,t,x;
  cin>>n>>d>>t;
  vector<ll> v;
  for(int i=0; i<n; ++i){
    cin>>x;
    v.push_back(x);
  }
  ll a=2*(n+2*t*n);
  for(int i=0; i<v.size(); ++i){
    for(int j=0; j<v.size(); ++j){
      if(i!=j){
        ll b=v[i]-v[j];
        ll c=b%d;
        if(c==0){
          ll e=abs(b);
          ll f=e/d-1;
          ll g=2+t*2+f;
          ll h=2+2*t*2;
          ll y=h-g;
          a-=y;
        }
      }
    }
  }
  cout<<a/2<<endl;
  return 0;
}