#include <iostream>
#include <algorithm>

using namespace std;

int main() {

    //nacitani vstupu
    int N, K, moveDist = 0, middle, dist;
    cin >> N >> K;

    int * array = new int[N];
    for(int i = 0; i != N; i++)
    {
        cin >> array[i];
    }

    //serazeni
    sort(array, array + N);

    //posuny
    if(N % 2 == 1)
    {
        middle = array[N/2];
        dist = 1; //udava vzdalenost od stredu v poctu pitek

        //posuny smerem doprava u pitek blize
        for(int i = N/2 - 1; i >= 0; --i)
        {
            moveDist += abs(array[i] - (middle - dist * K));
            //cout << "-i: " << i << ", movedist: " << moveDist << endl;
            //cout << "middle - dist * K: " << middle - dist * K << endl;
            //cout << "array[i] - (middle - dist * K): " << array[i] - (middle - dist * K) << endl;
            ++dist;
        }

        dist = 1;

        for(int i = N/2 + 1; i != N; ++i)
        {
            moveDist += abs(array[i] - (middle + dist * K));
            //cout << "+i: " << i << ", movedist: " << moveDist << endl;
            ++dist;
        }
    }
    else
    {
        middle = array[N/2 - 1];
        dist = 1; //udava vzdalenost od stredu v poctu pitek

        //posuny smerem doprava u pitek blize
        for(int i = N/2 - 2; i >= 0; --i)
        {
            moveDist += abs(array[i] - (middle - dist * K));
            //cout << "-i: " << i << ", movedist: " << moveDist << endl;
            //cout << "middle - dist * K: " << middle - dist * K << endl;
            //cout << "array[i] - (middle - dist * K): " << array[i] - (middle - dist * K) << endl;
            ++dist;
        }

        dist = 1;

        for(int i = N/2; i != N; ++i)
        {
            moveDist += abs(array[i] - (middle + dist * K));
            //cout << "+i: " << i << ", movedist: " << moveDist << endl;
            ++dist;
        }
    }

    cout << moveDist << endl;

    delete[] array;

    return 0;
}