#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
#include <iostream>
#include <cmath>
#include <iomanip>
#include <vector>
#include <stack>
#include <queue>
#include <list>
#include <map>
#include <vector>
#include <bitset>
#include <string>
#include <algorithm>
#include <iterator>
#include <unordered_map>
#include <unordered_set>
#include <sstream>
#include <fstream>
#include <numeric>
#include <tuple>
#include <ctime>
#include <random>
#include <array>
#include <cassert>
#include <complex>
#include <valarray>
#include <set>
#include <chrono>
using namespace std;
#define sorti(a) sort((a).begin(), (a).end());
#define reversi(a) reverse((a).begin(), (a).end());
#define yes cout << "Yes\n";
#define no cout << "No\n";
#define ans(a) cout << a << '\n';
#define read(a, n) {(a).resize(n); for (auto &i : a) cin >> i;}
//#define int long long
using ll = long long;
using ld = long double;
using ull = unsigned long long;
const int INF = 2147483647;
const ll LONGINF = 9223372036854775807;
const ll MOD = 1e9 + 7;
void solve()
{
int n;
ll h;
cin >> n >> h;
ll res = 0;
priority_queue<ll> pql;
pql.push(-1e9);
priority_queue<ll, vector<ll>, greater<>> pqr;
for (int i = 0; i < n; ++i)
{
ll a;
cin >> a;
ll x = pql.top() - h * i;
if (a == x)
{
pql.push(a + h * i);
pqr.push(a - h * i);
}
else if (a > x)
{
pqr.push(a - h * i);
pqr.push(a - h * i);
ll x = pqr.top() + h * i;
pqr.pop();
pql.push(x + h * i);
res += a - x;
}
else
{
pql.push(a + h * i);
pql.push(a + h * i);
ll x = pql.top() - h * i;
pql.pop();
pqr.push(x - h * i);
res += x - a;
}
}
ans(res)
}
signed main()
{
cin.tie(0)->sync_with_stdio(0);
int t = 1;
//cin >> t;
while (t--) solve();
return 0;
}
