#include <bits/stdc++.h>
using namespace std;
int main() {
  double n, d;
  double arr[2001];
  cin >> n >> d;
  int cnt = 0;
  for (int i = 0; i < n; ++i) {
    cin >> arr[i];
    if (i >= 1) {
      while (arr[i] <= arr[i - 1]) {
        double tmp = ceil((arr[i - 1] - arr[i]) / d);
        if (tmp == 0) {
          cnt += 1;
          arr[i] += d;
        } else {
          cnt += tmp;
          arr[i] += tmp * d;
        }
      }
    }
  }
  cout << cnt << endl;
  return 0;
}
