#include <iostream>
#include <algorithm>
#define MOD 1000000007

#define ll long long

using namespace std;

ll arr[1000000];
int n;
int d;

ll labs(ll a){
    return a<0?-a:a;
}

ll lmin(ll a, ll b){
    return a<b?a:b;
}

ll shift(int beg){
    ll sum = 0;
    ll pos = beg;
    for (int i=0;i<n;i++){
        sum += labs(arr[i]-pos);
        pos += d;
    }
    return sum;
}

int main(){
    cin >> n >> d;
    
    for(int i=0;i<n;i++){
        cin >> arr[i];
    }

    sort(arr, arr+n);

    ll sum = 0;
    for(int i=0;i<n;i++){
        sum += arr[i];
    }
    double avg = sum / (double) n;
    int low = (int) avg;
    int low_shift = ((n-1)*d)/2;

    // ll m = (2000000 * (long long)2000000);
    // m = lmin(m, shift(low - low_shift));
    // m = lmin(m, shift(low + 1 - low_shift));
    // m = lmin(m, shift(low - 1 - low_shift));

    // for(int i=arr[0]; i<=arr[n-1]; i++){
    //     cout << shift(i) << " ";
    // }
    // cout << endl;

    int l = arr[0];
    int r = arr[n-1];
    ll m = (2000000 * (long long)2000000);
    while (l!=r) {
        if (r-l < 20) {
            for(int i=arr[0]; i<=arr[n-1]; i++){
                m = lmin(m, shift(i));
            }
            break;
        }

        int m1 = l/3+2*r/3;
        int m2 = 2*l/3+r/3;
        ll lval = shift(l);
        ll rval = shift(r);
        ll m1val = shift(m1);
        ll m2val = shift(m2);
        // cout << l << " " << m1 << " " << m2 << " " << r << endl;
        // cout << lval << " " << m1val << " " << m2val << " " << rval << endl;
        if (lval < m1val) r = m1;
        else if (rval < m2val) l = m2;
        else if (m1val < m2val) r = m2;
        else if (m1val > m2val) l = m1;
        else {
            l = m1;
            r = m2;
        }
    }

    cout << m << endl;
}