A. Increasing Sequence

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概述

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

解题说明：题目的要求是通过每次对数列中的某个数增加d，让这个数列从小到大按序排列，问最少增加多少次d。做法是从前往后依次遍历，判断前后两个数的差值，如果前一个数大于后面的数，增加后面的数值，统计次数即可。

#include <iostream>
#include<algorithm>
#include<cstdio>
#include <cstring>
#include<string>
using namespace std;

int main()
{
	int n,m,i,d,a[100000],c=0;
	scanf("%d%d",&n,&d);
	for(i=0;i<n;i++)
	{
		scanf("%d",&a[i]);
	}
	for(i=0;i<n-1;i++)
	{
		if(a[i]>=a[i+1])
		{
			m=(a[i]-a[i+1])/d;
			m++;
			c+=m;
			a[i+1]+=m*d;
		}
	}
	printf("%dn",c);
	return 0;
}