#include <iostream>
#include <stdio.h>
#include <vector>
#include <algorithm>
//
// Created by cteam022 on 10/19/19.
//
using namespace std;

int checkSoul(vector<int> &original, vector<int> &new_seq, int shift) {
    int result = 0;
    for(int i = 0; i < original.size(); i++) {
        result += abs(original[i] - new_seq[i] - shift);
    }
    return result;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);

    int number, distance, temp, best_move = INT32_MAX;
    cin >> number >> distance;
    vector<int> sequence(number);

    for(int i = 0; i < number; i++) {
        cin >> temp;
        sequence[i] = temp;
    }

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

    vector<int> new_sequence(number);
    new_sequence[0] = sequence[0];
    for(int i = 1; i < number; i++) {
        new_sequence[i] = new_sequence[i-1] + distance;
    }

    int diff = new_sequence[number-1] - sequence[number-1];
    if(diff < 0) {
        for(int i = 0; i < (-1)*diff; i++) {
            temp = checkSoul(sequence, new_sequence, i);
            if(temp <= best_move) {
                best_move = temp;
            }else{
                break;
            }
        }
    }else if (diff >= 0){
        for(int i = 0; i < diff; i++) {
            temp = checkSoul(sequence, new_sequence, -1*i);
            if(temp <= best_move) {
                best_move = temp;
            }else{
                break;
            }
        }
    }else{
        return -1;
    }

    cout << best_move << endl;
    return 0;
}
// 10 4
// 140 26 69 55 39 64 2 89 78 421