#include<bits/stdc++.h>
using namespace std;
#include "boxes.h"
#define ll long long
long long delivery(int N, int K, int L, int p[]) {
sort(p, p+N);
if(K==1){
ll ans=0;
for(int i=0;i<N;i++){
ans+=2*min(p[i],L-p[i]);
}
return ans;
}
ll minCW[N+1] = {};
ll minCCW[N+1] = {};
//int cntCW[N+1] = {};
minCW[1] = 2*p[0];
for(int i=2;i<=N;i++){
if(i>K) minCW[i] = minCW[i-K] + 2*p[i-1];
else minCW[i] = minCW[i-1] + 2*(p[i-1]-p[i-2]);
//cout<<minCW[i]<<" ";
}
//cout<<endl;
minCCW[1] = 2*(L-p[N-1]);
for(int i=2;i<=N;i++){
if(i>K) minCCW[i] = minCCW[i-K] + 2*(L-p[N - i]);
else minCCW[i] = minCCW[i-1] + 2*(-p[N-i]+p[N-i+1]);
//cout<<minCCW[i]<<" ";
}
ll mina = (N+K-1)/K * (ll)L;
//cout<<endl;
//cout<<mina<<endl;
for(int i=0;i<=N;i++){
//cout<<i<<" "<<minCW[i] + minCCW[N-i]<<endl;
mina = min(mina, minCW[i] + minCCW[N-i]);
if(i+K<=N){
//cout<<"a "<<minCW[i] + L + minCCW[N-K-i]<<endl;
mina = min(mina, minCW[i] + L + minCCW[N-K-i]);
}
}
//cout<<endl;
//cout<<mina<<endl;
return mina;
}
