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\n",ans);
return 0;
}
