cf 11A

A. Increasing Sequence

time limit per test

1 second

memory limit per test

64 megabytes

input

standard input

output

standard output

A sequence a0, a1, ..., at - 1 is called increasing if ai - 1 < ai for each i: 0 < i < t.

You are given a sequence b0, b1, ..., bn - 1 and a positive integer d. In each move you may choose one element of the given sequence and add d to it. What is the least number of moves required to make the given sequence increasing?

Input

The first line of the input contains two integer numbers n and d (2 ≤ n ≤ 2000, 1 ≤ d ≤ 106). The second line contains space separated sequence b0, b1, ..., bn - 1 (1 ≤ bi ≤ 106).

Output

Output the minimal number of moves needed to make the sequence increasing.

Sample test(s)

input

4 2
1 3 3 2

output

3

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int n,d,a[2010],ans;
int main()
{
      scanf("%d%d",&n,&d);
      for(int i=0;i<n;i++)
            scanf("%d",&a[i]);
      for(int i=0;i<n-1;i++)
      {
            if(a[i+1]<=a[i])
            {
                  ans+=(a[i]-a[i+1])/d+1;
                  a[i+1]+=((a[i]-a[i+1])/d+1)*d;
            }
      }
      printf("%d
",ans);
      return 0;
}