#include<iostream>
#include<cmath>
using namespace std;
int main(void){
  int n,d,t;
  cin>>n>>d>>t;
  int x[101];
  for( int i = 0; i < n; i++ ){
    cin>>x[i];
  }
  int sum = (t*2+1) * n;
  for( int i = 0; i < n; i++ ){
    for( int j = i+1; j < n; j++ ){
      int dst = (int)abs(x[i]-x[j]);
      if( dst%d == 0 ){
        int tmp = 2*t-(dst/d) + 1;
        if(tmp>0) sum-=tmp;
      }
    }
  }
  cout<<sum<<endl;
  return 0;
}