#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 2e5 + 100;
int n;
ll h;
priority_queue<ll> pqLeft;
priority_queue<ll, vector<ll>, greater<ll>> pqRight;
ll ans = 0;
ll a[MAXN];
int main() {
cin >> n >> h;
for (int i = 0; i < n; i++) cin >> a[i];
pqLeft.push(a[0]); pqRight.push(a[0]);
for (int i = 1; i < n; i++) {
ll range = ((ll)i) * h; // mimic shifting left side by -h, and right side by h
// minimum area in graph is interval [pqLeft.top() - range; pqRight.top() + range]
ll minFrom = pqLeft.top() - range;
ll minTo = pqRight.top() + range;
if (a[i] < minFrom) {
pqLeft.push(a[i] + range);
pqLeft.push(a[i] + range);
ans += minFrom - a[i];
pqRight.push(pqLeft.top() - 2*range);
pqLeft.pop();
} else if (a[i] > minTo) {
pqRight.push(a[i] - range);
pqRight.push(a[i] - range);
ans += a[i] - minTo;
pqLeft.push(pqRight.top() + 2*range);
pqRight.pop();
} else {
pqLeft.push(a[i] + range);
pqRight.push(a[i] - range);
}
}
cout << ans << "\n";
return 0;
}
