#include "boxes.h"
#include <bits/stdc++.h>
using namespace std;
long long delivery(int N, int K, int L, int p[]) {
vector<int> left, right;
for (int i = 0; i < N; i++)
if (p[i] <= L / 2) {
left.push_back(p[i]);
} else
right.push_back(p[i]);
// cerr << left.size() << " " << right.size() << "\n";
// cout << (left.empty() ? 0 : left.back() * 2) +
// (right.empty() ? 0 : (N - right.front()) * 2)
// << "\n";
return min(L, (left.empty() ? 0 : left.back() * 2) +
(right.empty() ? 0 : (L - right.front()) * 2));
long long ans = 0;
for (int i = K - 1; i < left.size(); i += K) {
ans += 2 * left[i];
}
for (int i = K - 1; i < right.size(); i += K) {
ans += 2 * (L - right[i]);
}
if (left.size()) ans += (left.size() % K + right.size() % K + K - 1) / K;
return ans;
}
