#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i, n) for (int i = 0; i < (int) (n); i++)
#define reps(i, n) for (int i = 1; i <= (int) (n); i++)
#define all(x) (x).begin(), (x).end()
#define uniq(x) (x).erase(unique(all(x)), (x).end())
#define bit(n) (1LL << (n))
#define dump(x) cerr << #x " = " << (x) << endl
using vint = vector<int>;
using vvint = vector<vint>;
using pint = pair<int, int>;
using vpint = vector<pint>;
template<typename T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
constexpr double PI = 3.1415926535897932384626433832795028;
constexpr int DY[9] = {0, 1, 0, -1, 1, 1, -1, -1, 0};
constexpr int DX[9] = {1, 0, -1, 0, 1, -1, -1, 1, 0};
int sign(int x) { return (x > 0) - (x < 0); }
int gcd(int a, int b) {
    while (b) { swap(a %= b, b); }
    return a;
}
int lcm(int a, int b) { return a / gcd(a, b) * b; }
int cdiv(int a, int b) { return (a - 1 + b) / b; }
template<typename T> void fin(T mes) {
    cout << mes << endl;
    exit(0);
}
template<typename T, typename U> bool chmax(T &a, const U &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template<typename T, typename U> bool chmin(T &a, const U &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}
template<typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &rhs) {
    os << "(" << rhs.first << ", " << rhs.second << ")";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const vector<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const deque<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const set<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T, typename U> ostream &operator<<(ostream &os, const map<T, U> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
struct setup {
    static constexpr int PREC = 20;
    setup() {
        cout << fixed << setprecision(PREC);
        cerr << fixed << setprecision(PREC);
    };
} setup;

struct union_find_tree {
    std::vector<int> par, size;
    union_find_tree(int n) : par(n), size(n) {
        for (int i = 0; i < n; i++) {
            par[i] = i;
            size[i] = 1;
        }
    }
    int get_root(int i) {
        if (par[i] == i) { return i; }
        else { return par[i] = get_root(par[i]); }
    }
    void unite(int i, int j) {
        if ((i = get_root(i)) == (j = get_root(j))) { return; }
        if (size[i] < size[j]) { std::swap(i, j); }
        par[j] = i;
        size[i] += size[j];
    }
    bool are_same(int i, int j) { return get_root(i) == get_root(j); }
    int get_size(int i) { return size[get_root(i)]; }
};

template<typename M>
struct segment_tree {
    using T = typename M::T;
    int n;
    std::vector<T> data;
    segment_tree(int n) : n(n), data(n << 1, M::id()) {}
    segment_tree(const std::vector<T> &src) : n(src.size()), data(n << 1) {
        std::copy(src.begin(), src.end(), data.begin() + n);
        for (int i = n - 1; i > 0; i--) { data[i] = M::op(data[i << 1 | 0], data[i << 1 | 1]); }
    }
    void set(int i, const T &x) {
        data[i += n] = x;
        while (i >>= 1) { data[i] = M::op(data[i << 1 | 0], data[i << 1 | 1]); }
    }
    const T &operator[](int i) const { return data[i + n]; }
    T get_sum(int l, int r) const {
        T a = M::id(), b = M::id();
        for (l += n, r += n; l < r; l >>= 1, r >>= 1) {
            if (l & 1) { a = M::op(a, data[l++]); }
            if (r & 1) { b = M::op(data[--r], b); }
        }
        return M::op(a, b);
    }
};

int INF = 1e17;
struct rminq {
    using T = pint;
    static T op(const T &a, const T &b) { return std::min(a, b); }
    static T id() { return {INF, INF}; }
};

signed main() {
    int N, D;
    cin >> N >> D;
    vint A(N), L(N), R(N);
    vpint Ai(N);
    rep(i, N) { cin >> A[i], L[i] = A[i] - i * D, R[i] = A[i] + i * D, Ai[i] = {A[i], i}; }
    sort(all(Ai));
    vector<tuple<int, int, int>> edges;
    segment_tree<rminq> stL(N), stR(N);
    rep(i, N) { stL.set(i, {INF, i}), stR.set(i, {INF, i}); }
    for (auto[_, i]:Ai) {
        auto[wl, l]=stL.get_sum(0, i);
        auto[wr, r]=stR.get_sum(i + 1, N);
        if (l != INF) { edges.emplace_back(wl + R[i], l, i); }
        if (r != INF) { edges.emplace_back(L[i] + wr, i, r); }
        stL.set(i, {L[i], i}), stR.set(i, {R[i], i});
    }
    sort(all(edges));
    int ans = 0;
    union_find_tree uf(N);
    for (auto[w, u, v]:edges) {
        if (!uf.are_same(u, v)) { ans += w, uf.unite(u, v); }
    }
    cout << ans << endl;
}


Measured memory_bytes: 36016