// Jai Shree Ram
#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for(int i=a;i<n;i++)
#define ll long long
#define int long long
#define pb push_back
#define all(v) v.begin(),v.end()
#define endl "\n"
#define x first
#define y second
#define gcd(a,b) __gcd(a,b)
#define mem1(a) memset(a,-1,sizeof(a))
#define mem0(a) memset(a,0,sizeof(a))
#define sz(a) (int)a.size()
#define pii pair<int,int>
#define hell 1000000007
#define elasped_time 1.0 * clock() / CLOCKS_PER_SEC
template<typename T1,typename T2>istream& operator>>(istream& in,pair<T1,T2> &a){in>>a.x>>a.y;return in;}
template<typename T1,typename T2>ostream& operator<<(ostream& out,pair<T1,T2> a){out<<a.x<<" "<<a.y;return out;}
template<typename T,typename T1>T maxs(T &a,T1 b){if(b>a)a=b;return a;}
template<typename T,typename T1>T mins(T &a,T1 b){if(b<a)a=b;return a;}
int solve(){
int n,h;cin>>n>>h;
int ans=0;
priority_queue<int>left;
priority_queue<int,vector<int>,greater<int>>right;
int x;cin>>x;
left.push(x);
right.push(x);
rep(i,1,n){
cin>>x;
int shift = i*h;
int l = left.top()-shift;
int r = right.top()+shift;
if(x<l){
ans+=abs(x-l);
left.pop();
left.push(x+shift);
left.push(x+shift);
right.push(l-shift);
}
else if(x>r){
ans+=abs(x-r);
right.pop();
right.push(x-shift);
right.push(x-shift);
left.push(r+shift);
}
else{
left.push(x+shift);
right.push(x-shift);
}
}
cout<<ans<<endl;
return 0;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
#ifdef SIEVE
sieve();
#endif
#ifdef NCR
init();
#endif
int t=1;//cin>>t;
while(t--){
solve();
}
return 0;
}
