#include "boxes.h"
#include <bits/stdc++.h>
using namespace std;
int calc(int S[], int midl, int midr, int K, int N, int L) {
int cnt=0, comp=0;
for (int i = midl; i >= 0; --i)
{
if (cnt==0) comp+=S[i]*2;
cnt++;
if (cnt==K) cnt=0;
}
cnt=0;
for (int i = midr; i < N; ++i)
{
if (cnt==0) comp+=(L-S[i])*2;
cnt++;
if (cnt==K)cnt=0;
}
return comp;
}
long long delivery(int N, int K, int L, int p[]) {
sort(p, p+N);
int moit=L/2, mid=0;
if (N==1)
{
return min((L-p[0])*2, p[0]*2);
}
for (int i = 0; i < N; ++i)
{
if (p[i]<=moit) mid=p[i];
}
int l=mid, r=mid+1;
for (int i = 0; i < K; ++i)
{
if (l<0) r++;
else if (r>=N) l--;
else if (abs(p[l]-moit)<abs(p[r]-moit)) {
l--;
} else {
r++;
}
}
return min(L+calc(p, l, r, K, N, L), min(calc(p, mid, mid+1, K, N, L), calc(p, mid-1, mid, K, N, L)));
}
