#include <bits/stdc++.h>
using namespace std;
int n, d, a[2005], cnt;
double s;
int main() {
  scanf("%d%d", &n, &d);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
  }
  s = double(d);
  for (int i = 1; i < n; i++) {
    if (a[i] == a[i + 1]) {
      cnt++;
      a[i + 1] += d;
    } else if (a[i] > a[i + 1]) {
      while (a[i] >= a[i + 1]) {
        double m = ceil((a[i] - a[i + 1]) / s);
        a[i + 1] += (m * d);
        cnt += m;
        if (a[i] == a[i + 1]) {
          a[i + 1] += d;
          cnt++;
        }
      }
    }
  }
  printf("%d\n", cnt);
  return 0;
}
