#include <bits/stdc++.h>
using namespace std;
using ll = long long;

#define REP(i,n) for(long long i = 0; i < (n); i++)
#define FOR(i, m, n) for(long long i = (m);i < (n); ++i)
#define ALL(obj) (obj).begin(),(obj).end()

template<class T> using V = vector<T>;
template<class T, class U> using P = pair<T, U>;

const ll MOD = (ll)1e9 + 7;
const ll MOD2 = 998244353;
const ll LLINF = (ll)1e18;
const ll INTINF = (ll)1e9;
const long double PI = 3.1415926535897932384626433;

template <class T> void corner(bool flg, T hoge) {if (flg) {cout << hoge << endl; exit(0);}}
template <class T, class U>ostream &operator<<(ostream &o, const map<T, U>&obj) {o << "{"; for (auto &x : obj) o << " {" << x.first << " : " << x.second << "}" << ","; o << " }"; return o;}
template <class T>ostream &operator<<(ostream &o, const set<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const vector<T>&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;}
template <class T, class U>ostream &operator<<(ostream &o, const pair<T, U>&obj) {o << "{" << obj.first << ", " << obj.second << "}"; return o;}
template <template <class tmp>  class T, class U> ostream &operator<<(ostream &o, const T<U> &obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr)o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
void print(void) {cout << endl;}
template <class Head> void print(Head&& head) {cout << head;print();}
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) {cout << head << " ";print(forward<Tail>(tail)...);}
template <class T> void chmax(T& a, const T b){a=max<T>(a,b);}
template <class T> void chmin(T& a, const T b){a=min<T>(a,b);}
void YN(bool flg) {cout << ((flg) ? "YES" : "NO") << endl;}
void Yn(bool flg) {cout << ((flg) ? "Yes" : "No") << endl;}
void yn(bool flg) {cout << ((flg) ? "yes" : "no") << endl;}

template<class T> class Segment_Tree_Range_Minimum_Query {
public:
	int N;
	T ini;
	vector<T> node;

	Segment_Tree_Range_Minimum_Query(const vector<T> & ar, const T ini) : ini(ini) {
		for (N = 1; N < ar.size(); N *= 2);
		node.resize(2 * N - 1, ini);
		for (int i = 0; i<ar.size(); ++i) node[i + N - 1] = ar[i];
		for (int i = N - 2; i >= 0; --i) node[i] = min(node[2 * i + 1], node[2 * i + 2]);
	}

	void update(int idx, const T var) {
		idx += (N - 1);
		node[idx] = var;
		while (idx > 0) {
			idx = (idx - 1) / 2;
			node[idx] = min(node[2 * idx + 1], node[2 * idx + 2]);
		}
	}

	T getvar(const int a, const int b, int k = 0, int l = 0, int r = -1) {
		if (r < 0) r = N;
		if (r <= a || b <= l) return ini;
		if (a <= l && r <= b) return node[k];
		T vl = getvar(a, b, 2 * k + 1, l, (l + r) / 2);
		T vr = getvar(a, b, 2 * k + 2, (l + r) / 2, r);
		return min(vl, vr);
	}
};

//Union Find Tree
class Union_Find_Tree {
public:
	vector<int> parent;
    vector<int> rank;

    Union_Find_Tree(int N = 1) : parent(N), rank(N,0){
		for (int i = 0; i < N; ++i) parent[i] = i;
	}
 
	int root(int n) {
		return (parent[n] == n ? n : parent[n] = root(parent[n]));
	}

    bool same(int n, int m) {
		return root(n) == root(m);
	}
 
	void unite(int n, int m) {
		n = root(n);
		m = root(m);
		if (n == m) return;
		if(rank[n]<rank[m]) {
            parent[n] = m;
        }
        else{
            parent[m] = n;
            if(rank[n] == rank[m]) rank[n]++;
        }
	}
};

int main() {
	ll N,D; cin >> N >> D;
	V<ll> A(N); REP(i,N) cin >> A[i];
	V<P<ll,int>> ord(N);
	REP(i,N) ord[i] = {A[i],i};
	sort(ALL(ord));
	V<P<ll,int>> tmp(N+2,{LLINF,0});
	Segment_Tree_Range_Minimum_Query<P<ll,int>> SegL(tmp,{LLINF,0}), SegR(tmp,{LLINF,0});
	priority_queue<P<ll,P<int,int>>,V<P<ll,P<int,int>>>,greater<P<ll,P<int,int>>> >pq; 
	REP(i,N){
		int idx = ord[i].second;

		SegL.update(idx,{A[idx]-D*idx,idx});
		auto L = SegL.getvar(0,idx);
		auto l = L.second;
		if(L.first!=LLINF) pq.push({D*abs(l-idx)+A[l]+A[idx],{l,idx}});
		
		SegR.update(idx,{A[idx]+D*idx,idx});
		auto R = SegR.getvar(idx+1,N);
		auto r = R.second;
		if(R.first!=LLINF) pq.push({D*abs(idx-r)+A[idx]+A[r],{idx,r}});
	}
	Union_Find_Tree uf(N);
	ll ans = 0;
	while(pq.size()){
		auto e = pq.top();
		pq.pop();
		ll cost = e.first;
		int l = e.second.first;
		int r = e.second.second;
		if(uf.same(l,r)) continue;
		else uf.unite(l,r);
		ans += cost;
	}
	cout << ans << endl;

	


	return 0;
}


Measured memory_bytes: 34796