#line 1 "main.cpp"
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cstdint>
#include <cstdlib>
#include <cmath>
#include <complex>
#include <chrono>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>
#include <random>
#include <utility>
#include <limits>
#include <list>

/* template start */
 
#define rep(i, a, b) for (long long i = (a); (i) < (b); (i)++)
#define all(i) i.begin(), i.end()

#ifdef LOCAL
#define debug(...) std::cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

void debug_out(){std::cerr<<std::endl;}

template<typename Head,typename... Tail>
void debug_out(Head h,Tail... t){
  std::cerr<<" "<<h;
  if(sizeof...(t)>0)std::cout<<" :";
  debug_out(t...);
}
 
template <typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}
 
template <typename T>
std::ostream& operator<<(std::ostream& os, std::vector<T> vec) {
  for (std::size_t i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}
 
template<typename T1,typename T2>
inline bool chmax(T1& a,T2 b){return a<b && (a=b,true);}
 
template<typename T1,typename T2>
inline bool chmin(T1& a,T2 b){return a>b && (a=b,true);}

template<typename Num>
constexpr Num mypow(Num a, long long b) {
  if(b==0)return 1;
  if (a==0)return 0;
  Num x = 1;
  while (b > 0) {
    if(b & 1)x*=a;
    a*=a;
    b >>= 1;
  }
  return x;
}

template <std::uint_fast64_t Modulus> class modint {
  using u64 = std::uint_fast64_t;

public:
  u64 a;

  constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
  constexpr u64 &value() noexcept { return a; }
  constexpr const u64 &value() const noexcept { return a; }
  constexpr bool operator==(const modint rhs) const noexcept {return a==rhs.a;}
  constexpr bool operator!=(const modint rhs) const noexcept {return !(*this==rhs);}
  constexpr modint operator+(const modint rhs) const noexcept {
    return modint(*this) += rhs;
  }
  constexpr modint operator-(const modint rhs) const noexcept {
    return modint(*this) -= rhs;
  }
  constexpr modint operator*(const modint rhs) const noexcept {
    return modint(*this) *= rhs;
  }
  constexpr modint operator/(const modint rhs) const noexcept {
    return modint(*this) /= rhs;
  }
  constexpr modint &operator+=(const modint rhs) noexcept {
    a += rhs.a;
    if (a >= Modulus) {
      a -= Modulus;
    }
    return *this;
  }
  constexpr modint &operator-=(const modint rhs) noexcept {
    if (a < rhs.a) {
      a += Modulus;
    }
    a -= rhs.a;
    return *this;
  }
  constexpr modint &operator*=(const modint rhs) noexcept {
    a = a * rhs.a % Modulus;
    return *this;
  }
  constexpr modint &operator/=(modint rhs) noexcept {
    u64 exp = Modulus - 2;
    while (exp) {
      if (exp % 2) {
        *this *= rhs;
      }
      rhs *= rhs;
      exp /= 2;
    }
    return *this;
  }
};

/* template end */

using ll = long long;

struct Monoid{
  using value_t=std::pair<ll,ll>;
  static constexpr value_t id={1e18,-1};
  static constexpr value_t op(value_t a,value_t b){
    return (a.first<=b.first)?a:b;
  }
};

#line 2 "/mnt/c/Users/Imperi/Documents/cp-library/lib/SegmentTree/SegmentTree.cpp"

#line 5 "/mnt/c/Users/Imperi/Documents/cp-library/lib/SegmentTree/SegmentTree.cpp"

//Monoid
// type value_t
// static var id
// static (value_t,value_t)->value_t op

template<typename Monoid>
class SegmentTree{
  public:
  using value_t=typename Monoid::value_t;
  using size_t=std::size_t;

  private:
  size_t n,n0;
  std::vector<value_t> dat;

  public:
  SegmentTree(size_t n_):n(n_){
    assert(n_>0);
    n0=1;
    while(n0<n)n0<<=1;
    dat=std::vector<value_t>(2*n0-1,Monoid::id);
  }

  SegmentTree(const std::vector<value_t>& tmp):n(tmp.size()){
    assert(n>0);
    n0=1;
    while(n0<n)n0<<=1;
    dat=std::vector<value_t>(2*n0-1,Monoid::id);
    for(long long i=0;i<n;i++)dat[i+n0-1]=tmp[i];
    for(long long i=n0-2;i>=0;i--)dat[i]=Monoid::op(dat[2*i+1],dat[2*i+2]);
  }

  void update(size_t i,value_t val,bool change){
    assert(0<=i&&i<n);
    std::size_t now=i+n0-1;
    if(change)dat[now]=val;
    else dat[now]=Monoid::op(dat[now],val);

    while(now>0){
      now=(now-1)>>1;
      dat[now]=Monoid::op(dat[2*now+1],dat[2*now+2]);
    }
  }

  value_t fold(size_t a,size_t b){
    assert(0<=a&&a<=b&&b<=n);
    value_t rval=Monoid::id,lval=Monoid::id;
    size_t l=a+n0-1,r=b+n0-1;
    for(;l<r;l>>=1,r>>=1){
      if(!(r&1)){
        r--;
        rval=Monoid::op(dat[r],rval);
      }
      if(!(l&1)){
        lval=Monoid::op(lval,dat[l]);
        l++;
      }
    }

    return Monoid::op(lval,rval);
  }
};
#line 2 "/mnt/c/Users/Imperi/Documents/cp-library/lib/UnionFind/UnionFind.cpp"

#include <cstddef>
#line 6 "/mnt/c/Users/Imperi/Documents/cp-library/lib/UnionFind/UnionFind.cpp"

class UnionFind{
  public:
  using size_t=std::size_t;
  private:
  std::vector<size_t> par,sz;
  size_t group;

  public:

  UnionFind(size_t n=0):par(n,0),sz(n,1),group(n){
    std::iota(par.begin(),par.end(),0);
  }

  size_t root(size_t n){
    if(par[n]==n)return n;
    return par[n]=root(par[n]);
  }

  bool unite(size_t a,size_t b){
    a=root(a);b=root(b);
    if(a==b)return false;
    group--;
    if(sz[a]<sz[b])std::swap(a,b);
    sz[a]+=sz[b];
    par[b]=a;
    return true;
  }

  size_t size(){return par.size();}
  size_t groups(){return group;}
  size_t group_size(size_t n){return sz[root(n)];}

  bool same(size_t a,size_t b){return root(a)==root(b);}
};
#line 147 "main.cpp"

int main() {
  std::cin.tie(nullptr);
  std::ios::sync_with_stdio(false);

  ll n,d;
  std::cin>>n>>d;

  using P=std::pair<ll,ll>;

  std::vector<P> city(n);

  rep(i,0,n){
    std::cin>>city[i].first;
    city[i].second=i;
  }

  std::sort(all(city));

  SegmentTree<Monoid> left(n),right(n);

  std::vector<std::pair<ll,P>> edge;

  for(const auto& e:city){
    P l=left.fold(0,e.second);
    if(l.second!=-1)edge.emplace_back(l.first+e.first+d*e.second,P(l.second,e.second));
    P r=right.fold(e.second+1,n);
    if(r.second!=-1)edge.emplace_back(r.first+e.first-d*e.second,P(e.second,r.second));
    left.update(e.second,{e.first-d*e.second,e.second},true);
    right.update(e.second,{e.first+d*e.second,e.second},true);
  }

  std::sort(all(edge));

  ll ans=0;
  UnionFind uni(n);

  for(const auto& e:edge){
    if(!uni.same(e.second.first,e.second.second)){
      ans+=e.first;
      uni.unite(e.second.first,e.second.second);
    }
  }

  std::cout<<ans<<"\n";

  return 0;
}
