#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 S[]) {
sort(S, S+N);
if (N==1)
{
return min((L-S[0])*2, S[0]*2);
}
vector<long long> l, r;
for (int i = 0; i < N; ++i)
{
l.push_back(min(2*S[i], L));
l.back()+=((i-K>=0)?l[i-K]:0);
}
for (int i = N-1; i >= 0; --i)
{
r.push_back(min(2*(L-S[i]), L));
r.back()+=(((N-1)-i-K>=0)?r[(N-1)-i-K]:0);
}
long long res=r[N-1];
for (int i = 0; i < N-1; ++i)
{
res=min(res, l[i]+r[N-i-2]);
}
return min(res, l[N-1]);
}
