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

pair<int,int> tree[1<<11];

void update(int v,int val,int indx){
    tree[v]={val,indx};
    while (v/2>0){
        v/=2;
        tree[v]=max(tree[v*2],tree[v*2+1]);
    }
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int N,K;
    cin>>N>>K;
    int tab[N];
    for (int i=0;i<N;i++){
        cin>>tab[i];
        update(i+(1<<10),tab[i],i);
    }
    long long ans=0;
    for (int i=0;i<N;i++){
        pair<int,int> akt=tree[1];
        int wartosc=akt.first;
        int index=akt.second;
       // cout<<wartosc<<"\n";
        if (index+1<N and tab[index+1]<tab[index]){
            if (abs(tab[index]-tab[index+1])>K){
                ans+=tab[index]-K-tab[index+1];
                update(index+1+(1<<10),tab[index]-K,index+1);
                tab[index+1]=tab[index]-K;
            }
        }
        if (index-1>=0 and tab[index-1]<tab[index]){
            if (abs(tab[index]-tab[index-1])>K){
                ans+=tab[index]-K-tab[index-1];
                update(index-1+(1<<10),tab[index]-K,index-1);
                tab[index-1]=tab[index]-K;
            }
        }
        update(index+(1<<10),-1,-1);
    }
    cout<<ans<<"\n";
}