#include <bits/stdc++.h>

using namespace std;
using ll = long long;
#define SZ(a) (int)((a).size())
#define FOR(a, b, c) for(int a = b; a < c; ++a)
const int N = 1e6 + 7;

ll p[N];




int main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    ll n, k; cin >> n >> k;
    vector<ll> a(n);
    for(auto& i : a) cin >> i;
    sort(a.begin(), a.end());


    vector<ll> zmiana;
    ll a0 = -1e12;

    ll res = 0;
    FOR(i, 0, n) {
        p[i] = a0 + k * i;
        
        res += abs(p[i] - a[i]);

        if(p[i] <= a[i]) {
            zmiana.push_back(a[i] - p[i]);
        }
    }

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

    // for(auto& i : zmiana) cerr << i << " ";
    // cerr << "\n";

    ll ob = res, lastA = a0;
    int i = 0;
    while(i < SZ(zmiana)) {
        // cerr << lastA << " " << ob << "\n";
        int p = i;
        while(i + 1 < SZ(zmiana) and zmiana[i + 1] == zmiana[i]) {
            i++;
        }

        ll roz = zmiana[i] - (lastA - a0);
        ob = ob + n * roz - 2 * roz * (SZ(zmiana) - p);
        res = min(res, ob);
        lastA += roz;
        i++;
    }


    

    cout << res << "\n";
}