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

#define D if(0)

const int NMAX = 1123456;

struct Bod
{
	ll poz;
	ll posunO;
};

int n;
ll k;
Bod b[NMAX];

int main()
{
	scanf("%d%lld",&n,&k);
	for(int i=0;i<n;i++)
	{
		scanf("%lld",&(b[i].poz));
	}
	sort(b,b+n,[](Bod a,Bod b)->bool{return a.poz<b.poz;});
	for(int i=0;i<n;i++)
	{
		b[i].posunO=i*k-b[i].poz;
	}
	sort(b,b+n,[](Bod a,Bod b)->bool{return a.posunO<b.posunO;});
	ll posKor = b[n/2].posunO;
	ll out=0;
	for(int i=0;i<n;i++)
	{
		out += abs(b[i].posunO-posKor);
	}
	printf("%lld\n",out);
}