#include "boxes.h"
#include <bits/stdc++.h>
long long delivery(int N, int K, int L, int p[])
{
long long ans;
K = std::min(K, N);
std::vector<long long> dist1, dist2;
dist1.push_back(0), dist2.push_back(0);
dist1.reserve(N / 2), dist2.reserve(N / 2);
for (int i = 0; i < N; ++i)
if (p[i] <= L / 2)
dist1.push_back(p[i]);
else
dist2.push_back(L - p[i]);
sort(dist1.begin(), dist1.end()), sort(dist2.begin(), dist2.end());
int a = (int)dist1.size(), b = (int)dist2.size();
std::vector<long long> pref1(a, 0), pref2(b, 0);
for (int i = 1; i < a; ++i)
pref1[i] = dist1[i] + ((i >= K) ? pref1[i - K] : 0);
for (int i = 1; i < b; ++i)
pref2[i] = dist2[i] + ((i >= K) ? pref2[i - K] : 0);
ans = 2 * (pref1[a - 1] + pref2[b - 1]);
return ans;
}
