#include <bits/stdc++.h>   using namespace std;   long long s[1000005];   int main(void) {     int n, d, ans = 0;     cin >> n >> d >> s[1];     for (int i = 2; i <= n; ++i) {       cin >> s[i];       int cnt = 0;       if (s[i] <= s[i - 1]) cnt = (s[i - 1] - s[i] + d) / d;       s[i] += cnt * d;       ans += cnt;     }     return cout << ans <<   n , 0;   }   