#include<bits/stdc++.h>
using namespace std;
#define int long long
#define in array<int, 2>
#define pb push_back
#define pob pop_back
#define INF (int)1e17
#define MX (int)3e5+5
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL)
signed main()
{
fast();
int n, h; cin >> n >> h;
vector<int> a(n+1);
for(int i = 1; i <= n; i++)
cin >> a[i];
priority_queue<int> L, R; //R stores the negation of elements.
int B = -a[1];
L.push(a[1]); R.push(-a[1]); int ltag, rtag; ltag = rtag = 0;
//if x in set S, then x+stag is real value stored.
for(int i = 2; i <= n; i++)
{
rtag+=h; ltag-=h; B-=(R.size()*h); B-=a[i];
int zer = L.top()+ltag; int zer2 = rtag-R.top();
if(a[i] <= zer)
{
L.push(a[i]-ltag); L.push(a[i]-ltag);
R.push(-(L.top()+ltag-rtag)); L.pop();
//R.push(-(L.top()+ltag-rtag)); L.pop();
}
else if(a[i] >= zer2)
{
R.push(rtag-a[i]); R.push(rtag-a[i]);
L.push(rtag-R.top()-ltag); R.pop();
//L.push(rtag-R.top()-ltag); R.pop();
}
else
{
R.push(rtag-a[i]);
L.push(a[i]-ltag);
}
}
vector<int> v;//we shall find all the R change points, exact values.
while(R.size())
{
v.pb(rtag-R.top());
R.pop();
}
reverse(v.begin(), v.end());
int res = B;
for(auto x: v)
res+=x;
cout << res << "\n";
return 0;
}
