#include<bits/stdc++.h>
#include "boxes.h"
#define MAXN 10000007
using namespace std;
const long long inf=1e17;
int n,k,L;
int team[MAXN];
long long pref[MAXN],suff[MAXN],ans;
int cost(int l,int r){
int a=min(team[l],L-team[r]);
int c=team[r]-team[l];
return min(2*(a+c),L);
}
long long delivery(int N, int K, int LL,int p[]) {
n=N; k=K; L=LL;
for(int i=1;i<=n;i++){
team[i]=p[i-1];
}
pref[0]=0;
for(int i=1;i<=n;i++){
pref[i]=pref[max(i-k,0)]+cost(max(i-k+1,1),i);
}
suff[n+1]=0;
for(int i=n;i>=1;i--){
suff[i]=suff[min(i+k,n+1)]+cost(i,min(i+k-1,n));
}
ans=inf;
for(int i=0;i<=n;i++){
ans=min(ans,pref[i]+suff[i+1]);
}
if(n<=k)ans=min(ans,L+0LL);
return ans;
}
/*int main(){
cout<<delivery(3,2,8,{1,2,5})<<"\n";
return 0;
}*/
