#include <bits/stdc++.h>
int main() {
  int i, n, d, asd[2000], count = 0;
  scanf("%d %d", &n, &d);
  for (i = 0; i < n; i++) {
    scanf("%d", &asd[i]);
    if (i == 0)
      continue;
    else {
      if (asd[i] > asd[i - 1])
        continue;
      else {
        if (asd[i] == asd[i - 1]) {
          asd[i] += d;
          count++;
        } else if (asd[i] < asd[i - 1]) {
          int temp = (asd[i - 1] - asd[i]);
          count += (temp / d) + 1;
          asd[i] += d * ((temp / d) + 1);
        }
      }
    }
  }
  printf("%d", count);
  return 0;
}
