#include <vector>
#include <iostream>
#include <cmath>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <fstream>
#include <unistd.h>
#include <string.h>
#include <string>
#include <numeric>
#include <queue>
#include <deque>
#include <sstream>
#include <iomanip>
#include <set>
#include <stack>
#include <cassert>
#include <functional>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<char> vc;
typedef vector<vector<char>> vvc;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<vvd> vvvd;
typedef pair<ll, ll> PL;
typedef vector<PL> vpl;
typedef vector<vector<PL>> vvpl;
const int INF = 1001001001;
const ll LINF = 1e17;
const double pi = 3.1415926535897932;
const string endstr = "\n";
#define FOR(i, a, b) for(ll i = (a); i < b; i++)
#define RFOR(i, a, b) for(ll i = (a); i > b; i--)
#define rep(i, n) for(ll i = 0; i < n; i++)
#define rrep(i, n) for(ll i = n-1; i > -1; i--)
#define FORMAP(it, m) for(auto it = m.begin(); it != m.end(); it++)
#define ff first
#define ss second
#define pb push_back
#define epb emplace_back
#define ALL(X) (X).begin(),(X).end()

template <typename T>
T gcd(T a, T b) {
    return (a == 0) ? b : gcd(b%a, a);
}
template <typename T>
T lcm(T a, T b) {
    return a / gcd(a, b) * b;
}

bool p_comp_fs(const PL p1, const PL p2){ return p1.first < p2.first;};
bool p_comp_fg(const PL p1, const PL p2){ return p1.first > p2.first;};
bool p_comp_ss(const PL p1, const PL p2){ return p1.second < p2.second;};
bool p_comp_sg(const PL p1, const PL p2){ return p1.second > p2.second;};
template <typename T>
vector<T> uniquen(vector<T> vec){
    sort(ALL(vec));
    vec.erase(unique(vec.begin(), vec.end()), vec.end());
    return vec;
}

inline ll popcnt(ll x){return __builtin_popcountll((unsigned long long)x);};
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
//friend bool operator<(const stc& lhs, const stc& rhs){
//    return std::tie(lhs.l, lhs.r) < std::tie(rhs.l, rhs.r);
//}

struct UnionFind {
    vector<ll> par;
    
    UnionFind(ll n) : par(n, -1) { }
    void init(ll n) { par.assign(n, -1); }
    
    ll root(ll x) {
        if (par[x] < 0) return x;
        else return par[x] = root(par[x]);
    }
    
    bool issame(ll x, ll y) {
        return root(x) == root(y);
    }
    
    bool merge(ll x, ll y) {
        x = root(x); y = root(y);
        if (x == y) return false;
        if (par[x] > par[y]) swap(x, y); // merge technique
        par[x] += par[y];
        par[y] = x;
        return true;
    }
    
    ll size(ll x) {
        return -par[root(x)];
    }
};

vpl edgs;
vl A;
ll N, D;

void addEdge(ll l, ll r){
    if(r-l <= 1) return;
    ll m = (l+r)/2;
    ll ridx = -1, rmin = LINF;
    FOR(i, m, r){
        if(chmin(rmin, A[i]+i*D)) ridx = i;
    }
    FOR(i, l, m) edgs.pb({i, ridx});
    
    ll lidx = -1, lmin = LINF;
    FOR(i, l, m){
        if(chmin(lmin, A[i]-i*D)) lidx = i;
    }
    FOR(i, m, r) edgs.pb({i, lidx});
    addEdge(l, m);
    addEdge(m, r);
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> N >> D;
    A = vl(N); rep(i, N) cin >> A[i];
    addEdge(0, N);
    
    vector<pair<ll, PL>> m;
    for(auto e : edgs){
        ll c = A[e.ff] + A[e.ss] + D*abs(e.ff-e.ss);
        m.pb({c, e});
    }
    sort(ALL(m));
    
    ll ans = 0;
    auto uf = UnionFind(N);
    rep(i, m.size()){
        ll f = m[i].ss.ff, s = m[i].ss.ss;
        if(uf.issame(f, s)) continue;
        uf.merge(f, s);
        ans += m[i].ff;
    }
    cout << ans << endstr;
    return 0;
}


Measured memory_bytes: 183640