#include <bits/stdc++.h>
#include "boxes.h"
const int MAX_N = 10000000;
long long pref[1+MAX_N], suff[1+MAX_N];
long long cost(int i, int j, int l, int k, int n) {
return pref[i] + suff[j] + (long long)(n - i - j + k - 1) / k * l;
}
long long delivery(int n, int k, int l, int p[]) {
long long rez = 1LL << 60;
for(int i = 1; i <= n; ++i) {
if(i - k >= 0)
pref[i] = pref[i - k];
pref[i] = pref[i] + p[i - 1] * 2;
}
for(int i = 1; i <= n; ++i) {
if(i - k >= 0)
suff[i] = suff[i - k];
suff[i] = suff[i] + (l - p[n - i]) * 2;
}
if(k > n)
return l;
for(int i = 0; i <= n; ++i) {
rez = std::min(rez, cost(i, n - i, l, k, n));
if(n - i - k >= 0)
rez = std::min(rez, cost(i, n - i - k, l, k, n));
}
return rez;
}
