#include<bits/stdc++.h>
//ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//clock_t start=clock();clock_t end=clock();cout<<(double)(end-start)/CLOCKS_PER_SEC<<endl;
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef pair<int,int> pii;
typedef pair<pii,int> ppii;
typedef pair<int,pii> pipi;
typedef pair<ll,ll> pll;
typedef pair<pll,ll> ppll;
typedef pair<ll,pll> plpl;
typedef pair<pii,pii> pippi;
typedef tuple<ll,ll,ll> tl;
typedef pair<double,double> pdd;
typedef vector<vector<ll>> mat;
ll mod=1000000007;
ll mod2=998244353;
ll mod3=1000003;
ll mod4=998244853;
ll mod5=1000000009;
ll inf=1LL<<61;
int iinf=1<<30;
double pi=3.14159265358979323846;
double pi2=pi/2.0;
double eps=1e-8;
#define rep(i,m,n) for(ll i=m;i<n;i++)
#define rrep(i,n,m) for(ll i=n;i>=m;i--)
#define srep(itr,st) for(auto itr=st.begin();itr!=st.end();itr++)
#define mrep(itr,mp) for(auto& itr:mp)
#define Max(a,b) a=max(a,b)
#define Min(a,b) a=min(a,b)
//#define endl "\n"
int dh[4]={1,-1,0,0};
int dw[4]={0,0,1,-1};
int ddh[8]={-1,-1,-1,0,0,1,1,1};
int ddw[8]={-1,0,1,-1,1,-1,0,1};
struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        // http://xorshift.di.unimi.it/splitmix64.c
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
#define umh unordered_map<int,int,custom_hash>
ll gcd(ll a,ll b){
    if(a<0)a=-a;
    if(b<0)b=-b;
    if(a<b)swap(a,b);
    if(b==0)return a;
    if(a%b==0)return b;
    return gcd(b,a%b);
}
ll lcm(ll a,ll b){
    ll c=gcd(a,b);
    return a*b/c;
}
ll Pow(ll n,ll k){
    if(k<0)return 0;
    ll ret=1;
    ll now=n;
    while(k>0){
        if(k&1)ret*=now;
        now*=now;
        k/=2;
    }
    return ret;
}
ll beki(ll n,ll k,ll md){
  ll ret=1;
  ll now=n;
    now%=md;
  while(k>0){
    if(k%2==1){
      ret*=now;
      ret%=md;
    }
    now*=now;
    now%=md;
    k/=2;
  }
  return ret;
}
ll gyaku(ll n,ll md){
  return beki(n,md-2,md);
}
ll popcount(ll n){
    ll ret=0;
    ll u=n;
    while(u>0){
        ret+=u%2;
        u/=2;
        
    }
    return ret;
}
struct ST{
private:
    ll n;
    vector<pll> dat;
public:
    ST(vector<ll> v){
        ll sz=v.size();
        n=1;while(n<sz)n*=2;
        pll p={inf,inf};
        dat.resize(2*n-1,p);
        rep(i,0,sz)dat[i+n-1]={v[i],i};
        rrep(i,n-2,0){
            dat[i]=min(dat[i*2+1],dat[i*2+2]);
        }
    }
    void add(ll k,ll x){
        ll i=k+n-1;
        Min(x,dat[i].first);
        dat[i]={x,k};
        while(i>0){
            i=(i-1)/2;
            dat[i]=min(dat[2*i+1],dat[2*i+2]);
        }
    }
    pll que(ll a,ll b,ll k=0,ll l=0,ll r=-1){
        if(r<0)r=n;
        if(b<=l||a>=r)return {inf,inf};
        if(a<=l&&b>=r)return dat[k];
        pll m1=que(a,b,2*k+1,l,(l+r)/2);
        pll m2=que(a,b,2*k+2,(l+r)/2,r);
        return min(m1,m2);
    }
};
struct UF{
private:
    vector<int> par,len,you;
public:
    UF(int n){
        rep(i,0,n){
            par.push_back(i);
            len.push_back(0);
            you.push_back(1);
        }
    }
    int root(int n){
        if(par[n]==n)return n;
        else return par[n]=root(par[n]);
    }
    void unit(int a,int b){
        a=root(a);
        b=root(b);
        if(a==b)return;
        if(len[a]<len[b]){
            par[a]=b;
            you[b]+=you[a];
        }
        else{
            par[b]=a;
            you[a]+=you[b];
            if(len[a]==len[b])len[a]++;
        }
    }
    int yo(int a){
        a=root(a);
        return you[a];
    }
};
int main(){
    ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    ll n,d;cin>>n>>d;
    ll a[n];
    rep(i,0,n)cin>>a[i];
    UF uf(n);
    ll cnt=0;
    ll ans=0;
    for(;;){
        if(cnt==n-1)break;
        ST seg(vector<ll>(n,inf));
        ll mi[n];
        ll num[n];
        rep(i,0,n){
            ll ji=a[i]+i*d;
            ll g=uf.root(i);
            pll p=min(seg.que(0,g),seg.que(g+1,n));
            mi[i]=ji+p.first;
            num[i]=p.second;
            seg.add(g,a[i]-i*d);
        }
        ST seg2(vector<ll>(n,inf));
        rrep(i,n-1,0){
            ll ji=a[i]-i*d;
            ll g=uf.root(i);
            pll p=min(seg2.que(0,g),seg2.que(g+1,n));
            if(mi[i]>ji+p.first){
                num[i]=p.second;
                mi[i]=ji+p.first;
            }
            
            seg2.add(g,a[i]+i*d);
        }
        //rep(i,0,n)cout<<mi[i]<<" "<<num[i]<<endl;
        ll y[n];
        ll ynu[n];
        fill(y,y+n,inf);
        fill(ynu,ynu+n,inf);
        rep(i,0,n){
            ll g=uf.root(i);
            if(y[g]>mi[i]){
                y[g]=mi[i];
                ynu[g]=num[i];
            }
        }
        vector<pll> vv;
        rep(i,0,n){
            if(y[i]==inf)continue;
            ll ai=ynu[i];
            vv.push_back({y[i],i});
            
        }
        sort(vv.begin(),vv.end());
        rep(i,0,vv.size()){
            ll now=vv[i].second,ai=ynu[now];
            if(uf.root(now)!=uf.root(ai)){
                uf.unit(now,ai);
                ans+=vv[i].first;
                cnt++;
            }
        }
    }
    cout<<ans<<endl;
}


Measured memory_bytes: 35908