#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-8;
vector<string> split(const string& s, char c) {
  vector<string> v;
  stringstream ss(s);
  string x;
  while (getline(ss, x, c)) v.emplace_back(x);
  return move(v);
}
template <typename T, typename... Args>
inline string arrStr(T arr, int n) {
  stringstream s;
  s << "[";
  for (int i = 0; i < n - 1; i++) s << arr[i] << ",";
  s << arr[n - 1] << "]";
  return s.str();
}
inline void __evars_begin(int line) { cerr << "#" << line << ": "; }
template <typename T>
inline void __evars_out_var(vector<T> val) {
  cerr << arrStr(val, val.size());
}
template <typename T>
inline void __evars_out_var(T* val) {
  cerr << arrStr(val, 10);
}
template <typename T>
inline void __evars_out_var(T val) {
  cerr << val;
}
inline void __evars(vector<string>::iterator it) { cerr << endl; }
template <typename T, typename... Args>
inline void __evars(vector<string>::iterator it, T a, Args... args) {
  cerr << it->substr((*it)[0] == ' ', it->length()) << "=";
  __evars_out_var(a);
  cerr << "; ";
  __evars(++it, args...);
}
int n, d, res;
const int mxn = 1e6 + 10;
int a[mxn];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  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]) {
      continue;
    }
    int cnt = (a[i - 1] - a[i] + d) / d;
    res += cnt;
    a[i] += cnt * d;
  }
  cout << res << '\n';
  return 0;
}
