/*
ID: USACO_template
LANG: C++
PROG: https://oj.uz/problem/view/NOI18_safety
*/
#include <iostream> //cin , cout
#include <fstream> //fin, fout
#include <stdio.h> // scanf , pringf
#include <cstdio>
#include <algorithm> // sort , stuff
#include <stack> // stacks
#include <queue> // queues
#include <map>
#include <string>
#include <string.h>
#include <set>
using namespace std;
typedef pair<int, int> pii;
typedef vector<int> vi; /// adjlist without weight
typedef vector<pii> vii; /// adjlist with weight
typedef vector<pair<int,pii>> vpip; /// edge with weight
typedef long long ll;
#define mp make_pair
#define ff first
#define ss second
#define pb push_back
#define sz(x) (int)(x).size()
const int MOD = 1e9+7; // 998244353;
const int MX = 2e5+5; //
const ll INF = 1e18; //
#define MAXV 300007
#define MAXE 100007
bool debug;
int N;
ll H;
/// left and right side queue for the strictly increase/decrease array, with range of H.
priority_queue<ll> lq;
priority_queue<ll, vector<ll>, greater<ll>> rq;
int main() {
debug = false;
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> N >> H;
ll ans = 0LL;
for(int i=0;i<N;i++) {
ll a; cin >> a;
if(i==0) {
lq.push(a); rq.push(a);
continue;
}
ll range = (ll)i * (ll)H;
if(a + range < lq.top()) {
lq.push(a + range); /// max coverage
ans += lq.top() - (a + range); /// touch historical set by H
lq.push(a + range); /// compensate
rq.push(lq.top() - range * 2LL); /// also a possible option for right side
lq.pop();
} else if ( a - range > rq.top()) {
rq.push(a - range);
ans += (a - range) - rq.top();
rq.push(a - range);
lq.push(rq.top() + range *2LL);
rq.pop();
} else {
lq.push(a + range);
rq.push(a - range);
}
}
cout << ans << endl;
if(debug) cout << endl << "EOL" << endl;
}
/**
6 1
2 10 0 2 4 3
6 3
2 10 2 6 4 3
*/
