#include <cstdio>
#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n, d, pom, pom2, i, j, minWay = -1, w;

    int val[1000000];

    scanf("%d%d\n", &n, &d);

    for(int i = 0; i < n; i++){
        scanf("%d", &val[i]);
    }

    sort(val, val + n);

    for(i = 0; i < n; i++){
        w = 0;
        pom2 = 0 - i;


        for(j = 0; j < n; j++){
            if(i != j){
                pom = val[i] + pom2 * d - val[j];
                if(pom >= 0){
                    w += pom;
                }
                else{
                    w -= pom;
                }
            }
            pom2++;
        }

        if(w < minWay || minWay == -1){
            minWay = w;
        }



    }

    printf("%d", minWay);







    return 0;
}