codeforce 11 A

http://vjudge.net/contest/view.action?cid=18290#problem/A

Description

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

You are given a sequence b₀, b₁, ..., b_n - 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, ..., b_n - 1 (1 ≤ b_i ≤ 10⁶).

Output

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

Sample Input

Input

4 21 3 3 2

Output

3

一不小心就超时。。。

#include <stdio.h>#include <string.h>#include <iostream>using namespace std;int a[10005];int main(){    int n,d;    while(~scanf("%d%d",&n,&d))    {        for(int i=0; i<n; i++)            scanf("%d",&a[i]);        int sum=0;        for(int i=1; i<n; i++)        {            if(a[i]<=a[i-1])            {                int x=a[i-1]-a[i];                a[i]+=(x/d)*d;                sum+=x/d;                if(a[i]<=a[i-1])                {                    a[i]+=d;                    sum++;                }                if(a[i]<=a[i-1])                {                    a[i]+=d;                    sum++;                }            }        }        printf("%d\n",sum);    }    return 0;}