#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
int main() {
    long long n,k;
    cin>> n>>k;

    vector<long long > values;
    vector<long long > differences;

    long long start = 1000001;

    long long x;
    for (int i = 0; i < n; ++i) {
        cin >> x;
        values.push_back(x);
    }
    sort(values.begin(), values.end());

    for (int i = 0; i < n; ++i) {
        long long act_value = start + k * i;
        differences.push_back(act_value - values[i]);
    }

    sort(differences.begin(), differences.end());

    long long middle = differences[differences.size()/2];
    long long res = 0;
    for (int i = 0; i < n; ++i) {
        res += abs(values[i] - (start + k * i - middle));
    }


    std::cout << res << std::endl;
    return 0;
}