#include <iostream>
#include <algorithm>

using namespace std;

int main() {

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

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

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

    //posuny
    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));
        ++dist;
    }

    dist = 1;

    for (int i = N / 2 + 1; i < N; ++i) {
        moveDist += abs(array[i] - (middle + dist * K));
        ++dist;
    }

    cout << moveDist << endl;

    delete[] array;

    return 0;
}