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

using namespace std;

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

    int val[1000000];
    int way[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;
        pom = 1;
        way[i] = val[i];

        for(j = i - 1; j >= 0; j--){
            way[j] = way[i] - pom * d;
            pom++;
        }
        pom = 1;
        for(j = i + 1; j < n; j++){
            way[j] = way[i] + pom * d;
            pom++;
        }

        for(j = 0; j < n; j++){
            pom = way[j] - val[j];
            if(pom >= 0){
                w += pom;
            }
            else{
                w -= pom;
            }
        }

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



    }

    printf("%d", minWay);







    return 0;
}