#include<iostream>
#include<cstdio>
#include<cstring>
#include <cstdlib>  
#include <math.h>
#include <cmath>
#include<cctype>
#include<string>
#include<set>
#include<iomanip>
#include <map>
#include<algorithm>
#include <functional>
#include<vector>
#include<climits>
#include<stack>
#include<queue>
#include<bitset>
#include <deque>
#include <climits>
#include <typeinfo>
#include <utility> 
using namespace std;
using ll = long long;
template<typename T>using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
const ll inf = 1LL << 60;
#define all(x) (x).begin(),(x).end()
#define puts(x) cout << x << endl
#define rep(i,m,n) for(ll i = m;i < n;++i)
#define pb push_back
#define fore(i,a) for(auto &i:a)
#define rrep(i,m,n) for(ll i = m;i >= n;--i)

//segtree(min)
//initを忘れないこと！！！
struct Segmenttree {
	static const int N = 1 << 18;
	vector<ll>seg;
	vector<ll>idx;
	void st(ll p, ll v) {
		p += N - 1;
		seg[p] = v;
		idx[p] = p - N + 1;
		while (p > 0) {
			p = (p - 1) / 2;
			seg[p] = min(seg[2 * p + 1], seg[2 * p + 2]);
			if (seg[2 * p + 1] > seg[2 * p + 2])idx[p] = idx[2 * p + 2];
			else if (seg[2 * p + 1] < seg[2 * p + 2])idx[p] = idx[2 * p + 1];
			else idx[p] = min(idx[2 * p + 1], idx[2 * p + 2]);
		}
	}
	pair<ll, ll> query(ll l, ll r, ll a, ll b, ll k) {
		if (r <= a || b <= l)return { inf,inf };
		if (l <= a && b <= r)return { seg[k],idx[k] };
		ll m = (a + b) / 2;
		auto p1 = query(l, r, a, m, 2 * k + 1);
		auto p2 = query(l, r, m, b, 2 * k + 2);
		if (p1.first < p2.first) return p1;
		else if (p1.first > p2.first)return p2;
		else return { p1.first,min(p1.second,p2.second) };
	}

	void init() {
		seg.resize(2 * N);
		idx.resize(2 * N);
		for (int i = 0; i < 2 * N; i++)seg[i] = inf;
	}
	//[l,r]
	ll get(int l, int r) {
		return query(l, r + 1, 0, N, 0).first;
	}
	ll getidx(int l, int r) {
		return query(l, r + 1, 0, N, 0).second;
	}
	pair<ll, ll>getp(int l, int r) {
		return query(l, r + 1, 0, N, 0);
	}
};
//endsegtree

class UnionFind {
public:
	vector<int> r, p;

	UnionFind() {}
	UnionFind(int size) {
		r.resize(size, 0);
		p.resize(size, 0);
		rep(i, 0, size)makeSet(i);
	}

	void makeSet(int x) {
		p[x] = x;
		r[x] = 0;
	}

	bool same(int x, int y) {
		return findSet(x) == findSet(y);
	}

	void unite(int x, int y) {
		link(findSet(x), findSet(y));
	}

	void link(int x, int y) {
		if (r[x] > r[y]) {
			p[y] = x;
		}
		else {
			p[x] = y;
			if (x == y) {
				r[y]++;
			}
		}
	}


	int findSet(int x) {
		if (x == p[x]) {
			return x;
		}
		else {
			return p[x] = findSet(p[x]);
		}
	}
};


int main() {
	int N;
	ll D, A[202020];
	cin >> N >> D;
	for (int i = 0; i < N; i++)cin >> A[i];
	
	Segmenttree stL;
	Segmenttree stR;
	stL.init();
	stR.init();

	vector<int>order;
	for (int i = 0; i < N; i++)order.pb(i);
	sort(all(order), [&](int i, int j) {return A[i] < A[j]; });
	vector<vector<ll>>edges;

	fore(i, order) {
		auto p = stL.getp(0, i);
		if (p.first != inf) {
			ll cost = p.first + A[i] - (N - i)*D;
			edges.pb({cost,i,p.second});
		}
		p = stR.getp(i, N - 1);
		if (p.first != inf) {
			ll cost = p.first + A[i] - i * D;
			edges.pb({ cost,i,p.second });
		}
		stL.st(i, A[i]+(N-i)*D);
		stR.st(i, A[i] + i*D);
	}


	sort(all(edges));
	UnionFind uf(N);
	ll ans = 0;
	fore(e, edges) {
		if (!uf.same(e[1], e[2])) {
			uf.unite(e[1], e[2]);
			ans += e[0];
		}
	}
	puts(ans);

	return 0;
}

Measured memory_bytes: 44132