#include <bits/stdc++.h>
#define ADD(a, b) a = (a + ll(b)) % mod
#define MUL(a, b) a = (a * ll(b)) % mod
#define MAX(a, b) a = max(a, b)
#define MIN(a, b) a = min(a, b)
#define rep(i, a, b) for(int i = int(a); i < int(b); i++)
#define rer(i, a, b) for(int i = int(a) - 1; i >= int(b); i--)
#define all(a) (a).begin(), (a).end()
#define sz(v) (int)(v).size()
#define pb push_back
#define sec second
#define fst first
#define debug(fmt, ...) Debug(__LINE__, ":", fmt, ##__VA_ARGS__)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<int, pi> ppi;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> mat;
void Debug() {cout << '\n'; }
template<class FIRST, class... REST>void Debug(FIRST arg, REST... rest){
	cout<<arg<<" ";Debug(rest...);}
template<class T>ostream& operator<<(ostream& out,const vector<T>& v) {
	out<<"[";if(!v.empty()){rep(i,0,sz(v)-1)out<<v[i]<<", ";out<<v.back();}out<<"]";return out;}
template<class S, class T>ostream& operator<<(ostream& out,const pair<S, T>& v){
	out<<"("<<v.first<<", "<<v.second<<")";return out;}
const int MAX_N = 300010;
const int MAX_V = 100010;
const double eps = 1e-6;
const ll mod = 1000000007;
const int inf = 1 << 30;
const ll linf = 1LL << 60;
const double PI = 3.14159265358979323846;
///////////////////////////////////////////////////////////////////////////////////////////////////

struct UF {
	vector<int> par, ran;
	void init(int n) {
		par.resize(n); ran.resize(n);
		for(int i = 0; i < n; i++) {
			par[i] = i;
			ran[i] = 0;
		}
	}
	UF(int mx = 0) { init(mx); }

	int find(int x) {
		if(par[x] == x) return x;
		else return par[x] = find(par[x]);
	}
	void unite(int x, int y) {
		x = find(x);
		y = find(y);
		if(x == y) return;
		if(ran[x] < ran[y]) {
			par[x] = y;
		}
		else {
			par[y] = x;
			if(ran[x] == ran[y]) ran[x]++;
		}
	}
	bool same(int x, int y) { return find(x) == find(y); }
};

//////////////


struct edge { int u, v; ll cost; };

bool comp(const edge& e1, const edge& e2) {
	return e1.cost < e2.cost;
}

int N, E;
edge es[MAX_N * 2];

ll kruskal() {
	sort(es, es + E, comp);
	UF uf(N);//init union_find
	ll res = 0;
	for(int i = 0; i < E; i++) {
		edge e = es[i];
		if(!uf.same(e.u, e.v)) {
			uf.unite(e.u, e.v);
			res += e.cost;
		}
	}
	return res;
}

void add_edge(int s, int t, ll cost) {
	// debug(s, t, cost);
	es[E++] = edge{s, t, cost};
}

struct T {
	pl v;
	T(pl v = pl(linf, -1)) : v(v) {}
	T operator+(const T& t) { return T(min(v, t.v)); }
	friend ostream& operator<<(ostream& out, const T& t) {
		out << t.v; return out;
	}
};

struct segtree{
	int n; vector<T> seg;
	void init(int mx) {
		n = 1;
		while(n < mx) n *= 2;
		seg = vector<T>(n * 2);
	}
	segtree(int mx = 0) {
		init(mx);
	}
	void update(int i, T x) {
		i += n - 1;
		seg[i] = x;
		while(i > 0) {
			i = (i - 1) / 2;
			seg[i] = seg[i * 2 + 1] + seg[i * 2 + 2];
		}
	}
	T ga(int a, int b, int k, int l, int r) {
		if(b <= l || r <= a) return T();
		if(a <= l && r <= b) return seg[k];
		else {
			T lv = ga(a, b, k * 2 + 1, l, (l + r) / 2);
			T rv = ga(a, b, k * 2 + 2, (l + r) / 2, r);
			return lv + rv;
		}
	}
	void show() {
		vector<T> tmp;
		rep(i, 0, n) tmp.push_back(get(i, i + 1));
		debug(tmp);
	}
	//edit from here
	T get(int a, int b) { return ga(a, b, 0, 0, n); } //[a, b)
};

ll D;
ll A[MAX_N];
int idx[MAX_N];

void solve() {
	cin >> N >> D;
	rep(i, 0, N) cin >> A[i];
	rep(i, 0, N) idx[i] = i;
	sort(idx, idx + N, [&](int a, int b){ return A[a] < A[b]; });
	// debug(vi(idx, idx + N));
	segtree seg1(N);//Ai - D * i
	segtree seg2(N);//Ai + D * i

	rep(j, 0, N) {
		int i = idx[j];
		pl lp = seg1.get(0, i).v;
		pl rp = seg2.get(i + 1, N).v;
		if(lp.fst != linf) {
			add_edge(i, lp.sec, A[lp.sec] + A[i] + D * (i - lp.sec));
		}
		if(rp.fst != linf) {
			add_edge(i, rp.sec, A[i] + A[rp.sec] + D * (rp.sec - i));
		}
		seg1.update(i, T(pl(A[i] - D * i, i)));
		seg2.update(i, T(pl(A[i] + D * i, i)));
	}
	cout << kruskal() << "\n";
}

int main() {
#ifndef LOCAL
	ios::sync_with_stdio(false);
    cin.tie(0);
#endif
    cout << fixed;
	cout.precision(20);
	srand((unsigned int)time(NULL));
#ifdef LOCAL
	//freopen("in.txt", "wt", stdout); //for tester
    freopen("in.txt", "rt", stdin);
#endif	
	solve();
#ifdef LOCAL
    cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
#endif
	return 0;
}



Measured memory_bytes: 28160