#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned u;
typedef vector<int> vi;
typedef pair<int, int> pii;
#define F first;
#define S second;
#define PB push_back;
#define MP make_pair;

bool EQ(double a, double b) {
    return (fabs(a-b) / (a+b) < DBL_EPSILON);
}

vector<ll> points ;
ll  closest ( ll a) {
    ll idx = 0;
    ll dist = 999999;
    for ( ll i = 0 ; i < (ll)points.size() ; ++ i ) {
        if( abs(points[i] - a) < dist) {
            dist =  a - points[i];
            idx= i;
        }
    }
    return  idx;
}
void print()
{
    for ( auto & it : points )
        cout << it << " ";
    cout << endl;
}
ll  calcDist ( ll arr, ll dist , ll idx) {
    ll sum = 0;
    for ( ll i = 0 ; i < (ll)points.size() ; ++ i ) {
        int val = abs(points[i] - arr + (idx - i) * dist);
        //cout <<  val << endl;
        sum += val;
    }
    return sum;
}

ll sumMm () {
    ll sum = 0 ;
    for ( auto & it : points ) sum += it ;
    return sum;
}

int main( ) {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    // code
    size_t n , dist ;
    cin >> n >> dist ;
    for ( size_t  i = 0 ; i < n ; ++ i ) {
        ll tmp ;
        cin >> tmp ;
        points.push_back( tmp );
    }
    sort(points.begin(), points.end());
    ll closestI = n/2;
    ll arr = points[closestI];
    int res = calcDist(arr, dist, closestI);
    if(n % 2 == 0){
        ll closestI = n/2 -1;
        ll arr = points[closestI];
        int tmp = calcDist(arr, dist, closestI);
        if(tmp < res)
            res = tmp;
    }
    cout << res << endl;

    return 0;
}