#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, num, d;
  cin >> num >> d;
  int arr[num];
  for (i = 0; i < num; i++) {
    cin >> arr[i];
  }
  int temp, divi, rem, count = 0;
  for (i = 1; i < num; i++) {
    if (arr[i] > arr[i - 1])
      continue;
    else if (arr[i] == arr[i - 1]) {
      arr[i] = arr[i] + d;
      count++;
    } else {
      temp = arr[i - 1] - arr[i];
      divi = temp / d;
      divi++;
      arr[i] = arr[i] + (d * divi);
      count = count + divi;
    }
  }
  cout << count << endl;
  return 0;
}
