#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(i, a, n) for (int i = (a); i < (n); i++)
#define per(i, a, n) for (int i = (n) - 1; i >= (a); i--)
#define FOR(i, n) rep(i, 0, (n))
#define fi first
#define se second

char endl = '\n';
int main(void) {
    int N;
    ll K;
    scanf("%i %lld", &N, &K);
    ll a[N];
    int i;
    for(i=0;i<N;i++){
        scanf("%lld", &a[i]);
    }
    ll res=0;
    sort(a,a+N);
    if(N%2==0){
        for(i=0;i<N/2;i++){
            res+=abs((a[N/2]-(N/2-i)*K)-a[i])+abs((a[N/2]+(N/2-i-1)*K)-a[N-i-1]);
        }
    }
    else{
        for(i=0;i<N/2;i++){
            res+=abs((a[N/2]-(N/2-i)*K)-a[i])+abs((a[N/2]+(N/2-i)*K)-a[N-i-1]);
        }
    }
    printf("%lld\n", res);
	return 0;
}