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// n<=1000?
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pb push_back
#define ff first
#define ss second
#define INF 1000000001LL
#define POT (1LL<<23)
#define INFL 1000000000000000099LL
#define pii pair<ll,ll>
#define ppi pair<pii,ll>
#define pip pair<ll,pii>
#define ppp pair<pii,pii>
#define vi vector<ll>
#define vii vector<pii>
#define vvi vector<vi>
#define al(x) x.begin(),x.end()
#define rev(x) reverse(al(x))
#define X 18
#define FCTCST 7
template<typename T, typename U>
pair<T, U> operator+(const pair<T, U>& a, const pair<T, U>& b) {
    return {a.first + b.first, a.second + b.second};
}
template<typename T, typename U>
pair<T, U> operator-(const pair<T, U>& a, const pair<T, U>& b) {
    return {a.first - b.first, a.second - b.second};
}
template<typename T, typename U,typename Z>
pair<T, U> operator*(const pair<T, U>& a, const Z& b) {
    return {a.first*b, a.second*b};
}
template<typename T, typename U,typename Z>
pair<T, U> operator/(const pair<T, U>& a, const Z& b) {
    return {a.first/b, a.second/b};
}
template<typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os<<"{"<<p.ff<<", "<<p.ss<<"}";
    return os;
}
template<typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "{";
    for (size_t i = 0; i < v.size(); ++i) {
        if (i) os << ", ";
        os << v[i];
    }
    os << "}";
    return os;
}
template<ll MOD=998244353>
struct mint_t{
    ll x;
    mint_t(ll y=0){x=y%MOD;if(x<0)x+=MOD;}
    mint_t& operator+=(const mint_t& a){if((x+=a.x)>=MOD)x-=MOD;return *this;}
    mint_t& operator-=(const mint_t& a){if((x+=MOD-a.x)>=MOD)x-=MOD;return *this;}
    mint_t operator+(const mint_t& a)const{mint_t res(*this);return res+=a;}
    mint_t operator-(const mint_t& a)const{mint_t res(*this);return res-=a;}
    mint_t& operator*=(const mint_t& a){(x*=a.x)%=MOD;return *this;}
    mint_t operator*(const mint_t& a)const{mint_t res(*this);return res*=a;}
    mint_t fp(ll y)const{
        mint_t a=1,b=x;
        while(y){
            if(y&1)a*=b;
            b*=b;
            y/=2;
        }
        return a;
    }
    mint_t& operator/=(const mint_t& a){(*this)*=a.fp(MOD-2);return *this;}
    mint_t operator/(const mint_t& a)const{mint_t res(*this);return res/=a;}
};
#define mint mint_t<>
template<long long MOD>
istream& operator>>(istream& in, mint_t<MOD>& a){
    ll x;
    in>>x;
    a=mint_t<MOD>(x);
    return in;
}
template<long long MOD>
istream& operator<<(istream& out, mint_t<MOD>& a){
    out<<a.x;
    return out;
}
mint fct[FCTCST];
mint bnm(ll a,ll b){
    if(b>a || a<0)return 0;
    return fct[a]/fct[b]/fct[a-b];
}
bool vs[1001];
ll sm;
void solve(){
    ll n,k,a;
    cin>>n>>k;
    priority_queue<pii>q;
    for(ll i=0;i<n;i++){
        cin>>a;
        sm-=a;
        q.push({a,i});
    }
    
    while(q.size()){
        pii x=q.top();
        q.pop();
        if(vs[x.ss])continue;
        vs[x.ss]=1;
        sm+=x.ff;
        if(x.ss)q.push({x.ff-k,x.ss-1});
        if(x.ss<n-1)q.push({x.ff-k,x.ss+1});
    }
    cout<<sm;
}
int main(){
    ios_base::sync_with_stdio(0);
    fct[0]=1;
    for(ll i=1;i<FCTCST;i++)fct[i]=fct[i-1]*i;
    ll t=1;
    //cin>>t;
    for(ll i=1;i<=t;i++){
        //cout<<"Case #"<<i<<": ";
        solve();
    }
}