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

#define NDEBUG
#include <cassert>


typedef long long ll;
typedef long double Double;
typedef unsigned long long ull;
typedef pair<int,int> ii;
typedef pair<ll,ll> llll;
typedef pair<double,double> dd;

typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<llll> vllll;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<long double> vD;

#define sz(a)  int((a).size())
#define pb  push_back
#define eb  emplace_back
#define FOR(var,from,to) for(int var=(from);var<=(to);++var)
#define rep(var,n)  for(int var=0;var<(n);++var)
#define rep1(var,n)  for(int var=1;var<=(n);++var)
#define repC2(vari,varj,n)  for(int vari=0;vari<(n)-1;++vari)for(int varj=vari+1;varj<(n);++varj)
#define repC3(vari,varj,vark,n)  for(int vari=0;vari<(n)-2;++vari)for(int varj=vari+1;varj<(n)-1;++varj)for(int vark=varj+1;vark<(n);++vark)
#define ALL(c)  (c).begin(),(c).end()
#define RALL(c)  (c).rbegin(),(c).rend()
#define tr(i,c)  for(auto i=(c).begin(); i!=(c).end(); ++i)
#define found(s,e)  ((s).find(e)!=(s).end())
#define mset(arr,val)  memset(arr,val,sizeof(arr))
#define mid(x,y) ((x)+((y)-(x))/2)
#define IN(x,a,b) ((a)<=(x)&&(x)<=(b))
#define cons make_pair

template<class T> inline void amin(T & a, T const & b) { a = min(a, b); }
template<class T> inline void amax(T & a, T const & b) { a = max(a, b); }
template<typename X, typename T> auto vectors(X x, T a) { return vector<T>(x, a); }
template<typename X, typename Y, typename Z, typename... Zs> auto vectors(X x, Y y, Z z, Zs... zs) { auto cont = vectors(y, z, zs...); return vector<decltype(cont)>(x, cont); }


ll gcd(ll a, ll b) { while(a) swap(a, b%=a); return b; }

const ll MOD=1000000007LL;

ll ADD(ll x, ll y) { return (x+y) % MOD; }
ll SUB(ll x, ll y) { return (x-y+MOD) % MOD; }
ll MUL(ll x, ll y) { return x*y % MOD; }
ll POW(ll x, ll e) { ll v=1; for(; e; x=MUL(x,x), e>>=1) if (e&1) v = MUL(v,x); return v; }
ll DIV(ll x, ll y) { /*assert(y%MOD!=0);*/ return MUL(x, POW(y, MOD-2)); }

#define INTSPACE 12
char _buf[INTSPACE*1000000 + 3];

int loadint() {
    if (fgets(_buf, INTSPACE+3, stdin)==NULL) return 0;
    return atoi(_buf);
}

int loadvec(vector<int>& v, int N=-1) {
    if (N == 0) {
        v.clear();
        return 0;
    }
    if (N == -1) {
        N = loadint();
        if (N==0) return 0;
    }
    int bufsize = INTSPACE*N + 3;
    if (fgets(_buf, bufsize, stdin)==NULL) return 0;
    v.resize(N);

    int i=0;
    bool last = false;
    for (char *p=&_buf[0]; ;) {
        char *q = p;
        while (*q > ' ') ++q;
        if (*q == 0x0D || *q == 0x0A) last = true;
        *q = 0;
        v[i++] = atoi(p);
        if (last || i == N) break;
        p = q+1;
    }
    return i;
}
void read_cr() {
    fgets(_buf, 256, stdin);
}


int N;
ll D;
vi a;


vector<pair<ll,ii>> prepare(){
    vector<pair<ll,ii>> res;

    vll b(N), c(N);
    rep(i,N) {
        b[i] = D*i + a[i];
        c[i] = -D*i + a[i];
    }

    ll bmin = LLONG_MAX; int bmin_at;
    for (int i=N-1; i>=0; --i) {
        if (b[i] < bmin) {
            bmin = b[i]; bmin_at = i;
        }
    }
    for (int i=0; i<bmin_at; ++i) {
        ll cost = a[i] + a[bmin_at] + D*(bmin_at - i);
        res.emplace_back(cost, ii(i,bmin_at));
    }

    ll cmin = LLONG_MAX; int cmin_at;
    for (int i=0; i<N; ++i) {
        if (c[i] < cmin) {
            cmin = c[i]; cmin_at = i;
        }
    }
    for (int i=cmin_at+1; i<N; ++i) {
        ll cost = a[cmin_at] + a[i] + D*(i - cmin_at);
        res.emplace_back(cost, ii(cmin_at,i));
    }

    priority_queue<pair<ll,int>> pq;
    if (bmin_at < cmin_at) {
        for (int i=N-1; i>=0; --i) {
            if (i < N-1) {
                int j = pq.top().second;
                ll cost = (a[i] + a[j]) + D*(j-i);
                res.emplace_back(cost, ii(i,j));
            }
            pq.emplace( -b[i], i );
        }
    }

    return move(res);
}

class UnionFind {
 public:
  vector<int> data;
  int count;
 public:
  UnionFind(int size) : data(size, -1), count(size) { }
  bool unionSet(int x, int y) {
    x = root(x); y = root(y);
    if (x != y) {
      if (data[y] < data[x]) swap(x, y);
      data[x] += data[y]; data[y] = x;
      --count;
    }
    return x != y;
  }
  bool findSet(int x, int y) { return root(x) == root(y); }
  int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
  int size(int x) { return -data[root(x)]; }
};

ll solve() {
    priority_queue<pair<ll,ii>> pq;

    vector<pair<ll,ii>> l2r = prepare();
    for (auto &p : l2r) {
        ll cost = p.first;
        int i = p.second.first, j = p.second.second;
        pq.emplace(-cost, ii(i,j));
    }

    reverse(ALL(a));
    vector<pair<ll,ii>> r2l = prepare();
    for (auto &p : r2l) {
        ll cost = p.first;
        int i = p.second.first, j = p.second.second;
        pq.emplace(-cost, ii(N-1-j, N-1-i));
    }

    ll total = 0LL;
    UnionFind uf(N);
    int isles = N;
    while (!pq.empty()) {
        ll cost = -pq.top().first;
        int i = pq.top().second.first, j = pq.top().second.second;
        pq.pop();
        if (uf.root(i) != uf.root(j)) {
            total += cost;
            uf.unionSet(i,j); --isles;
            if (isles == 1) break;
        }
    }

    return total;
}

int main() {
    scanf("%d%lld", &N, &D); read_cr();
    a.resize(N);
    loadvec(a,N);
    cout << solve() << endl;
    return 0;
}
