#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int compare_ints(const void* a, const void* b)
{
    int arg1 = *(const int*)a;
    int arg2 = *(const int*)b;
 
    if (arg1 < arg2) return -1;
    if (arg1 > arg2) return 1;
    return 0;
}

int main(){
    int n, k, i;
    long double count = 0;
    scanf("%d %d", &n, &k);
    
    int booths[n];
    for(i=0;i<n;i++){
      int help;
      scanf("%d", &help);
      booths[i] = help;
    }
    
    int size = sizeof booths / sizeof *booths;
    qsort(booths, size, sizeof(int), compare_ints);
    
    int poz = round(n/2);
    int med = booths[poz];
    int helpme = med - (poz)*k;
    for (i=1;i<=n;i++){
	count = count + abs(booths[i-1]-helpme);
	helpme += k;
    }
    
    printf("%.0Lf", count);
    return 0;
}