#include <bits/stdc++.h>
using namespace std;

typedef long long int ll;
typedef double ld;

typedef pair<ll, ll> ii;
typedef vector<ll> vi;
typedef vector<ii> vii;

#define PB push_back
#define ff first
#define ss second
#define MP make_pair

#define FOR(prom, a, b) for ( ll prom = (a); prom < (ll)b; ++prom)
#define F(a) FOR(i,0,a)
#define FF(a) FOR(j, 0, a)

#define EPS (1e-10)
#define EQ(a, b) (fabs(a-b) <= fabs(a+b)*EPS)
#define LINF (1<<62LL)
#define DEB(x) cerr << ">>> " << #x << " ; " << x << "\n"

ll pozice[1000008];

int main()
{
    ll n,k,stred,potreba,potreba2;
    potreba = 0;
    potreba2 = 0;
    
    cin >> n >> k;
    F(n) cin >> pozice[i];
    sort(pozice, &pozice[n]);
    if(n%2==0)
    {
        stred = pozice[n/2];
        F(n/2) {potreba += abs(pozice[i] - (stred - ((n/2-i) * k))); /*cerr << potreba << endl;*/} 
        FOR(i,(n/2)+1,n) {potreba += abs(pozice[i] - ((k*(i-n/2)) + stred)); /*cerr << potreba << endl;*/} 
        
        stred = pozice[n/2+1];
        F(n/2+1) {potreba2 += abs(pozice[i] - (stred - ((n/2+1-i) * k))); /*cerr << potreba << endl;*/} 
        FOR(i,(n/2+1)+1,n) {potreba2 += abs(pozice[i] - ((k*(i-n/2+1)) + stred)); /*cerr << potreba << endl;*/}
        
        cout << min(potreba,potreba2) << endl;
        DEB(potreba);
        DEB(potreba2);
        return 0;
    }
    
    stred = pozice[n/2];
    F(n/2) {potreba += abs(pozice[i] - (stred - ((n/2-i) * k))); } 
    FOR(i,(n/2)+1,n) {potreba += abs(pozice[i] - ((k*(i-n/2)) + stred)); } 
    //F(n) cout << pozice[i] << endl;
    cout << potreba << endl;
     
    


return 0;
}