#include <bits/stdc++.h>
using namespace std;
const int dx[] = {0, -1, 0, 1};
const int dy[] = {1, 0, -1, 0};
long long mnx = 1e11, mxx = -1e11, mny = 1e11, mxy = -1e11;
double a[2010];
int ans = 0;
int main() {
  double n, d;
  cin >> n >> d;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (int i = 1; i < n; i++) {
    if (a[i] <= a[i - 1]) {
      double tmp = (a[i - 1] - a[i] + 1) / d;
      ans += ceil(tmp);
      a[i] += ceil(tmp) * d;
    }
  }
  cout << ans;
}
