/*
                                                                                                     
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          `:s+/:--....-::/+s-`      .-   `-                -`           -///:--------:/:`           
           ./s+//:::::://oo-``..НЕЙРОННУЮ: СЕТЬ:::::::-`РАБОТЯГИ        `+:--........--:/`          
            .:ooo+++++osso-`    `.:-...`/` ./::-------:/:`   -`         :+--..``````.--:+:...-+:-`  
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              `.:///////.-`      .:-..` -``-+o+/:::::/+o/.  `-         `:+:-..`````..--:o/:--/ys+-  
            `-++///////+o/. ``....`-.    :` `.:++++++/:.`  .-           -o/---......---/o.   `.`    
           `++//:-----::/+o:..`     .-`   :    ```````    .-           `+so+:--------:++-`          
  `````:-``:o/::-..`..--:/+o`         -.  `-             .-          `../../+o+////+o+:.`           
  -----syo/o+/:--.```..-://s.          .-` `-           .-        `...     ``-:////:-``             
       .` `/s//:--....-::/+s.            -. `-`        .-       `..`                                
           .+o+/:::--:://+s/-..`          .::+y  ```  .-     `..`                                   
            ./oo++////+oso-`   `....       :y-+:::::::/`   ...                                      
             `.:+oooooo/-`         `....-. .//:-------:/:-.`                                        
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                                         .+/--...```..--:+/`                                        
                                         `-o/:---...---:++.                                         
                                          `-+o+/:---:/+o/.                                          
                                            `.:+oooo+/-.`                                           
                                               ``````                                               
*/

#ifdef aimbot
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
#endif

#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <set>
#include <queue>
#include <ostream>
#include <istream>
#include <typeinfo>
#include <iomanip>
#include <cstdio>
#include <cstdlib>
#include <cassert>
#include <limits>
#include <fstream>
#include <array>
#include <list>
#include <bitset>
#include <functional>
#include <random>
#include <cstring>
#include <chrono>

#define random escape__from__random__aetuhoetnuhshe
#define mt make_tuple
#define x first
#define y second
#define pb push_back
#define ppb pop_back
#define mp make_pair
#define umap unordered_map
#define uset unordered_set
#define elif else if
#define len(v) ((int)v.size())
#define f(i, n) for (int i = 0; i < (n); i++)
#define rof(i, n) for (int i = ((n) - 1); i >= 0; i--) 
#define apply(v, act) for (auto &x : v) { act; }
#define log(args...) {string s = #args;deque<string> deq;\
string buf = "";int bal = 0;for (char c : s) {\
if (c == '(' || c == '[' || c == '{') {bal++;\
} else if (c == ')' || c == ']' || c == '}') {\
bal--;} else {if (bal == 0) {if (c == ',') {\
deq.pb(buf);buf = "";} else {if (c != ' ') {\
buf += c;}}}}}if (!buf.empty()) {deq.pb(buf);}\
smart_io::precall_print();smart_io::_print(deq, args);}

#define print    \
smart_io::precall_print(); \
cout,

#define scan cin,

#ifdef fast_allocator
const int MAXMEM = 200 * 1000 * 1024;
char _memory[MAXMEM];
size_t _ptr = 0;
void* operator new(size_t _x) { _ptr += _x; assert(_ptr < MAXMEM); return _memory + _ptr - _x; }
void operator delete (void*) noexcept {}
#endif

using namespace std;

char string_in_buffer[(int)260];


void fast_scan(int &x) { scanf("%d", &x); }
void fast_scan(long long &x) { scanf("%lld", &x); }
void fast_scan(unsigned long long &x) { scanf("%llu", &x); }
void fast_scan(double &x) { scanf("%lf", &x); }
void fast_scan(long double &x) { scanf("%Lf", &x); }
void fast_scan(char &x) { 
	scanf("%c", &x); 
	if (x == '\n') {
		fast_scan(x);
	}
}
void fast_scan(string &x) {
	scanf("%s", string_in_buffer);
	x = string(string_in_buffer);
}

template<class TFirst, class TSecond>
void fast_scan(pair<TFirst, TSecond> &p) {
	fast_scan(p.first);
	fast_scan(p.second);
}

template <class T>
void fast_scan(vector<T> &v) {
	for (auto &x : v) fast_scan(x);
}

void fast_print(const int &x) { printf("%d", x); }
void fast_print(const unsigned int &x) { printf("%u", x); }
void fast_print(const long long &x) { printf("%lld", x); }
void fast_print(const unsigned long long &x) { printf("%llu", x); }
void fast_print(const double &x) { printf("%.15lf", x); }
void fast_print(const long double &x) { printf("%.15Lf", x); }
void fast_print(const char &x) { printf("%c", x); };
void fast_print(const string &x) { printf("%s", x.c_str());}
void fast_print(const char v[]) { fast_print((string)v); }

template<class TFirst, class TSecond>
void fast_print(const pair<TFirst, TSecond> &p) {
	fast_print(p.first);
	fast_print(' ');
	fast_print(p.second);
}

template <class T>
void fast_print(const vector<T> &v) {
	if (v.empty()) return;
	fast_print(v[0]);
	for (int i = 1; i < v.size(); i++) {
		fast_print(' ');
		fast_print(v[i]);
	}
}

template <class T>
void fast_print(const vector<vector<T>> &v) {
	if (v.empty()) return;
	fast_print(v[0]);
	for (int i = 1; i < v.size(); i++) {
		fast_print('\n');
		fast_print(v[i]);
	}
}

template <class T>
void fast_print(const T &v) {
	for (const auto &x : v) {
		fast_print(x);
		fast_print(' ');
	}
}


using namespace std;


namespace smart_io {
	string print_start = "";
	string sep = " ";
	bool first_print = false;

	void precall_print() {
		fast_print(print_start);
		print_start = "\n";
		first_print = true;
	}

	void _print(deque<string>) {}
	template<class T, class... Args>
	void _print(deque<string> names, T elem, Args... args) {
		if (!first_print) {
			fast_print("\n");
		} else {
			first_print = false;
		}
		fast_print(names.front());
		fast_print(" = ");
		fast_print(elem);
		names.pop_front();
		_print(names, args...);
	}
} //namespace smart_io


template <class T>
ostream &operator,(ostream &os, const T &object) {
	if (!smart_io::first_print) {
		fast_print(smart_io::sep);
	} else {
		smart_io::first_print = false;
	}
	fast_print(object);
	return os;
}

template <class T>
istream &operator,(istream &is, T &object) {
	fast_scan(object);
	return is;
}

namespace random {
	using namespace std::chrono;
	mt19937 rng(duration_cast< milliseconds >(
		system_clock::now().time_since_epoch()
	).count());
	uniform_real_distribution<> prob_dist(0.0, 1.0);
};

namespace typedefs {
	typedef long long ll;
	typedef unsigned long long ull;
	typedef pair<int, int> pii;
	typedef long double ld;
}

namespace numbers_operation {
	template<class T>
	T floor_mod(T a, T b) {
		if (a >= 0 && b >= 0) return a % b;
		if (a <= 0 && b <= 0) return a % b;
		return abs(b) - (abs(a) % abs(b));
	}
}

using namespace numbers_operation;
using namespace typedefs;
using namespace random;

typedef pair<ll, int> Value;

Value INF = mp((ll)1e18, -1);

const int N = (1 << 18);

Value TP[2 * N + 1];
Value TN[2 * N + 1];

Value queryR(Value T[], int i, int tl, int tr, int R) {
	if (tr <= R) return T[i];
	if (tl >= R) return INF;
	int m = (tl + tr) / 2;
	return min(queryR(T, i * 2 + 1, tl, m, R), queryR(T, i * 2 + 2, m, tr, R));
}

Value queryL(Value T[], int i, int tl, int tr, int L) {
	if (tl >= L) return T[i];
	if (tr <= L) return INF;
	int m = (tl + tr) / 2;
	return min(queryL(T, i * 2 + 1, tl, m, L), queryL(T, i * 2 + 2, m, tr, L));
}

void update(Value T[], int i, Value value) {
	i += N - 1;
	T[i] = value;
	while (i > 0) {
		i = (i - 1) / 2;
		T[i] = min(T[i * 2 + 1], T[i * 2 + 2]);
		if (i == 0) break;
	}
}

int n;
ll D;

vector<int> a;

struct SUS {
	vector<vector<int>> comps;
	vector<int> up;
	int get_root(int v) {
		if (up[v] == v) return v;
		return up[v] = get_root(up[v]);
	}
	SUS(int n) {
		up.resize(n);
		comps.resize(n);
		f(i, n) {
			up[i] = i;
			comps[i].pb(i);
		}
	}
	void merge(int a, int b) {
		a = get_root(a);
		b = get_root(b);
		if (a == b) return;
		if (len(comps[a]) > len(comps[b])) swap(a, b);

		for (int x : comps[a]) {
			comps[b].pb(x);
		}
		comps[a].clear();
		comps[a].shrink_to_fit();

		up[a] = b;
	}
	bool one_comp(int a, int b) {
		return get_root(a) == get_root(b);
	}
};

signed main(signed argc, char *argv[]) {
	scan n, D;
	a.resize(n);
	scan a;

	SUS sus(n);

	ll result = 0;

	auto __min = [](pair<ll, int> a, pair<ll, int> b) {
		return min(a, b);
	};
	auto __apply_mod = [](pair<ll, int> value, pair<ll, int> mod, int, int) {
		return mod;
	};
	auto __merge_mods = [](pair<ll, int> a, pair<ll, int> b, int, int) {
		return b;
	};
	// TreeSegment<pair<ll, int>, pair<ll, int>, decltype(__min), decltype(__apply_mod), decltype(__merge_mods)> POS(n, mp((ll)1e18, -1), __min, __apply_mod, __merge_mods, mp(1LL, (int)1));
	// TreeSegment<pair<ll, int>, pair<ll, int>, decltype(__min), decltype(__apply_mod), decltype(__merge_mods)> NEG(n, mp((ll)1e18, -1), __min, __apply_mod, __merge_mods, mp(1LL, (int)1));


	vector<pair<ll, int>> edges(n);

	for (int i = 0; i < N; i++) {
		update(TP, i, INF);
		update(TN, i, INF);
	}

	for (int i = 0; i < n; i++) {
		update(TP, i, mp(D * (i + 1) + a[i], i));
		update(TN, i, mp(-D * (i + 1) + a[i], i));
	}
	int cnt = 0;
	while (true) {
		cnt++;
		int noempty = 0;
		f(i, n) {
			if (!sus.comps[i].empty()) {
				noempty++;
			}
		}
		if (noempty == 1) break;

		for (int i = 0; i < n; i++) {
			if (sus.comps[i].empty()) continue;
			edges[i] = mp((ll)1e18, -1);
			for (int j : sus.comps[i]) {
				update(TP, j, mp((ll)1e18, -1));
				update(TN, j, mp((ll)1e18, -1));
			}
			for (int j : sus.comps[i]) {
				auto c = queryR(TN, 0, 0, N, j);
				auto d = queryL(TP, 0, 0, N, j + 1);
				c.x += a[j] + (j + 1) * D;
				d.x += a[j] - (j + 1) * D;
				edges[i] = min(edges[i], min(c, d));
			}
			for (int j : sus.comps[i]) {
				update(TP, j, mp(D * (j + 1) + a[j], j));
				update(TN, j, mp(-D * (j + 1) + a[j], j));
			}
		}
		for (int i = 0; i < n; i++) {
			if (edges[i].second == -1) continue;
			int a = i;
			int b = edges[i].second;
			if (sus.one_comp(a, b)) continue;
			sus.merge(a, b);
			result += edges[i].first;
		}
	}
	// log(cnt);
	print result;
}


Measured memory_bytes: 34304