#include <bits/stdc++.h>
#include "boxes.h"
using namespace std;
long long delivery(int n, int k, int len, int p[]) {
vector<int> pos;
for (int i = 0; i < n; i++) {
if (p[i] > 0) {
pos.push_back(p[i]);
}
}
n = pos.size();
vector<int> l, r;
for (int i = 0; i < n; i++) {
if (pos[i] <= len / 2) {
l.push_back(pos[i]);
} else {
r.push_back(pos[i]);
}
}
ranges::reverse(r);
int left = l.size() % k + r.size() % k;
long long ans = 0;
if (left <= k) {
ans += len;
l.pop_back();
r.pop_back();
}
for (int i = k - 1; i < l.size(); i += k) {
ans += l[i] * 2;
}
for (int i = k - 1; i < r.size(); i += k) {
ans += (len - r[i]) * 2;
}
if (!l.empty()) ans += l.back() * 2;
if (!r.empty()) ans += (len - r.back()) * 2;
return ans;
}
