#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, k, a, ans=0;
cin>>n>>k>>a;
priority_queue<int> left;
priority_queue<int, vector<int>, greater<int> > right;
left.push(a);
right.push(a);
for (int i=1; i<n; ++i){
cin>>a;
if (a<left.top()-i*k){
left.push(a+i*k);
left.push(a+i*k);
ans+=abs(a-left.top()+i*k);
right.push(left.top()-2*i*k);
left.pop();
}
else if (a>right.top()+i*k){
right.push(a-i*k);
right.push(a-i*k);
ans+=abs(a-right.top()-i*k);
left.push(right.top()+2*i*k);
right.pop();
}
else left.push(a+i*k), right.push(a-i*k);
}
cout<<ans;
}
