// includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(st, itr) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define vrep(v, i) for(int i = 0; i < (v).size(); i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
#define dump(a, n) for(int i = 0; i < n; i++)cout << a[i] << "\n "[i + 1 != n];
#define dump2(a, n, m) for(int i = 0; i < n; i++)for(int j = 0; j < m; j++)cout << a[i][j] << "\n "[j + 1 != m];
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
typedef complex<double> cd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}

template<typename T, typename E>
struct SegmentTree_ {
  function<T(T, T)> f;
  function<T(T, E)> g;
  int n;
  T def;
  vector<T> vec;
  SegmentTree_(){}
  SegmentTree_(int n_, function<T(T, T)> f_, function<T(T, E)> g_, T def_, vector<T> v=vector<T>()){
    f = f_;
    g = g_;
    def = def_;

    // initialize vector
    n = 1;
    while(n < n_){
      n *= 2;
    }
    vec = vector<T>(2*n -1, def);

    // initialize segment tree
    for(int i = 0; i < v.size(); i++){
      vec[i + n - 1] = v[i];
    }
    for(int i = n - 2; i >= 0; i--){
      vec[i] = f(vec[2*i+1], vec[2*i+2]);
    }
  }
  void update(int k, E val){
    k = k + n - 1;
    vec[k] = g(vec[k], val);
    while(k > 0){
      k = (k - 1) / 2;
      vec[k] = f(vec[2*k+1], vec[2*k+2]);
    }
  }
  // [l, r) -> [a, b) (at k)
  T query(int a, int b, int k, int l, int r){
    if(r <= a || b <= l)return def;
    if(a <= l && r <= b)return vec[k];
    T ld = query(a, b, 2*k+1, l, (l+r)/2);
    T rd = query(a, b, 2*k+2, (l+r)/2, r);
    return f(ld, rd);
  }
  T query(int a, int b){
    return query(a, b, 0, 0, n);
  }
};

template<typename T, typename E>
using SegmentTree = struct SegmentTree_<T, E>;
using SegmentTreeI = SegmentTree<int, int>;
using SegmentTreeL = SegmentTree<long long, long long>;

typedef struct UnionFind_ {
  vector<int> par;
  vector<int> rank_;
  UnionFind_(int n): rank_(n, 0) {
    for(int i = 0; i < n; i++)par.push_back(i);
  }
  int find(int x) {
    if(par[x] == x)return x;
    else return par[x] = find(par[x]);
  }
  bool same(int x, int y) {
    if(find(x) == find(y))return true;
    else return false;
  }
  bool unite(int x, int y){
    int xp = find(x);
    int yp = find(y);
    if(xp == yp)return false;
    if(rank_[xp] > rank_[yp])par[yp] = xp;
    else if(rank_[xp] < rank_[yp])par[xp] = yp;
    else {
      par[yp] = xp;
      rank_[xp]++;
    }
    return true;
  }
} UnionFind;

template <typename T>
struct edge{
  int from;
  int to;
  T cost;
};

template <typename T>
bool comp(const edge<T> &a, const edge<T> &b){
  return a.cost < b.cost;
}

template <typename T>
struct Graph {
  int n;
  vector<edge<T>> es;
  Graph(int n_){
    n = n_;
  }
  void adde(int from, int to, T cost){
    es.push_back((edge<T>){from, to, cost});
  }
  T kruskal(){
    T res = 0;
    UnionFind uf(n);
    sort(es.begin(), es.end(), comp<T>);
    for(auto e: es){
      int from = e.from;
      int to = e.to;
      T cost = e.cost;
      if(uf.same(from, to))continue;
      res += cost;
      uf.unite(from, to);
    }

    return res;
  }
};

using GraphI = Graph<int>;

int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n;
  ll d;
  cin >> n >> d;
  vector<ll> a(n);
  cin >> a;
  vector<Pl> v(n);
  rep(i, n)v[i] = mk(a[i], i);
  sort(all(v));
  SegmentTree<Pl, Pl> segl = SegmentTree<Pl, Pl>(n, [](Pl a, Pl b){return a.FI < b.FI ? a: b;},
      [](Pl a,Pl b){return b;}, mk(linf, -1), vector<Pl>());
  SegmentTree<Pl, Pl> segr = SegmentTree<Pl, Pl>(n, [](Pl a, Pl b){return a.FI < b.FI ? a: b;},
      [](Pl a,Pl b){return b;}, mk(linf, -1), vector<Pl>());
  Graph<ll> graph(n);
  rep(i, n){
    int id = v[i].SE;
    ll ai = v[i].FI;
    auto p = segl.query(0, id);
    if(p.SE >= 0){
      graph.adde(id, p.SE, (ll)(id - p.SE) * d + ai + a[p.SE]);
      graph.adde(p.SE, id, (ll)(id - p.SE) * d + ai + a[p.SE]);
    }
    p = segr.query(id + 1, n);
    if(p.SE >= 0){
      graph.adde(id, p.SE, - (ll)(id - p.SE) * d + ai + a[p.SE]);
      graph.adde(p.SE, id, - (ll)(id - p.SE) * d + ai + a[p.SE]);
    }

    segl.update(id, mk(- (ll)id * d + ai, id));
    segr.update(id, mk((ll)id * d + ai, id));
  }
  cout << graph.kruskal() << endl;
  return 0;
}


Measured memory_bytes: 39656