#include <bits/stdc++.h>
#define fr(i, n, m) for(int i = (n); i < (m); i++)
#define pb push_back
#define st first
#define nd second
#define pq priority_queue
#define all(x) begin(x), end(x)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
const int mxn = 2e5+5;
const ll inf = 1e18;
const int i_inf = 1e9;
const ll mod = 1000003;
mt19937 _rand(time(NULL));
clock_t z;
//while((clock()-z)/CLOCKS_PER_SEC > 0.9)
int n;
ll k;
ll a[mxn];/*
struct p{
ll x, y;
ll delta;
};
vector<p> v1;
vector<p> v2;
void Shift(ll h){
fr(i, 0, (int)v1.size()){
v1[i].x -= h;
}
fr(i, 0, (int)v2.size()){
v2[i].x += h;
}
}
void Insert(ll h){
if(h <= v1.back().x){
fr(i, 0, (int)v2.size()){
++v2[i].delta;
}
fr(i, 0, (int)v1.size()){
if(h <= v1[i].x){
ll yh = v1[i].y + abs(v1[i].x - h)*v1[i].delta;
ll deltah = v1[i].delta+1;
fr(j, 0, i){
++v1[j].delta;
}
fr(j, i, (int)v1.size()){
--v1[j].delta;
}
p nov = v1.back();
nov.delta = 1;
v2.insert(v2.begin(), nov);
if(v1.back().delta == 0) v1.pop_back();
nov.x = h;
nov.y = yh;
nov.delta = deltah;
v1.insert(v1.begin()+i, nov);
break;
}
}
}
else if(h >= v2[0].x){
fr(i, 0, (int)v1.size()){
++v1[i].delta;
}
for(int i = (int)v2.size()-1; i >= 0; i --){
if(h >= v2[i].x){
ll yh = v2[i].y + abs(v2[i].x-h)*v2[i].delta;
ll deltah = v2[i].delta+1;
fr(j, 0, i+1){
--v2[j].delta;
}
fr(j, i+1, (int)v2.size()){
++v2[j].delta;
}
p nov;
nov.x = h;
nov.y = yh;
nov.delta = deltah;
v2.insert(v2.begin()+i+1, nov);
nov = v2[0];
nov.delta = 1;
v1.pb(nov);
if(v2[0].delta == 0) v2.erase(v2.begin());
break;
}
}
}
else{
fr(i, 0, (int)v1.size()){
v1[i].delta ++;
}
fr(i, 0, (int)v2.size()){
v2[i].delta ++;
}
p nov;
nov.y = v1.back().y;
nov.x = h;
nov.delta = 1;
v1.pb(nov);
v2.insert(v2.begin(), nov);
}
fr(i, 0, (int)v1.size()){
v1[i].y += abs(v1[i].x-h);
}
fr(i, 0, (int)v2.size()){
v2[i].y += abs(v2[i].x-h);
}
}
*/
int main(){
cin >> n >> k;
fr(i, 0, n){
cin >> a[i];
}
pq <ll> v1;
pq <ll> v2;
v1.push(a[0]);
v2.push(-a[0]);
ll ans = 0;
fr(i, 1, n){
ll vtop1 = v1.top();
ll vtop2 = -v2.top();
ll lef = vtop1 - i*k;
ll rig = vtop2 + i*k;
if(a[i] < lef){
ans += abs(lef-a[i]);
v1.push(a[i]+i*k);
v1.push(a[i]+i*k);
v1.pop();
v2.push(-(lef-i*k));
}
else if(a[i] > rig){
ans += abs(rig-a[i]);
v2.push(-(a[i]-i*k));
v2.push(-(a[i]-i*k));
v2.pop();
v1.push(rig+i*k);
}
else{
v1.push(a[i]+i*k);
v2.push(-(a[i]-i*k));
}
}
cout<<ans<<endl;
/*
p nov;
nov.x = a[0];
nov.y = 0;
nov.delta = 1;
v1.pb(nov);
v2.pb(nov);
fr(i, 1, n){
Shift(k);
Insert(a[i]);
}
cout<<v1.back().y<<endl;*/
}
