C :

#include<stdio.h>
#include<string.h>
long long a[2005];

int main()

{
    int n,d,i;
    while(~scanf("%d%d",&n,&d))
    {
        int sum = 0;
        memset(a,0,sizeof(a));
        for(i = 1;i <= n;i++)
        {
            scanf("%lld",&a[i]);
            if(a[i] > a[i - 1])
                continue;
            else
            {
                int t = a[i - 1] - a[i];
                a[i] = (t / d + 1) * d + a[i];
                sum += t / d + 1;
            }
        }
        printf("%d\n",sum);
    }
}

C++ :

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cctype>
#include<cmath>
#include<algorithm>
#include<iostream>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<stack>
#include<list>
#include<map>
#include<set>

#define TEST

#define LL long long
#define Mt(f, x) memset(f, x, sizeof(f));
#define rep(i, s, e) for(int i = (s); i <= (e); ++i)
#ifdef TEST
    #define See(a) cout << #a << " = " << a << endl;
    #define See2(a, b) cout << #a << " = " << a << ' ' << #b << " = " << b << endl;
    #define debug(a, s, e) rep(_i, s, e) {cout << a[_i] << ' ';} cout << endl;
    #define debug2(a, s, e, ss, ee) rep(i_, s, e) {debug(a[i_], ss, ee)}
#else
    #define See(a)
    #define See2(a, b)
    #define debug(a, s, e)
    #define debug2(a, s, e, ss, ee)
#endif // TEST

const int MAX = 2e9;
const int MIN = -2e9;
const double eps = 1e-8;
const double PI = acos(-1.0);

using namespace std;

int a[2005];

int main()
{
    int n, d;
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
    while(~scanf("%d%d", &n, &d))
    {
        int ans = 0;
        for(int i = 0; i < n; ++i)
        {
            scanf("%d", &a[i]);
        }
        for(int i = 1; i < n; ++i)
        {
            if(a[i - 1] >= a[i])
            {
                int t = (a[i - 1] - a[i]) / d + 1;
                a[i] += t * d;
                ans += t;
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}