#include "boxes.h"
#include <bits/stdc++.h>
using namespace std;
long long delivery(int N, int K, int L, int p[]) {
long long pref[N + 1], suff[N + 2];
memset(pref, 0, sizeof(pref));
memset(suff, 0, sizeof(suff));
// coba ke next atau ke 0
for(int i = 0; i < N; ++i) {
if(i % K == 0) {
// ambil dr posisi sebelumnya itu sum, dengan distance sekarang
if(i != 0)
pref[i] += min(p[i - 1], L - p[i - 1]);
pref[i + 1] = pref[i] + p[i];
}
else {
pref[i + 1] = pref[i] + p[i] - p[i - 1];
pref[i] += min(p[i - 1], L - p[i - 1]);
}
}
for(int i = N - 1; i >= 0; --i) {
if(i % K == (N - 1) % K) {
if(i != N - 1)
suff[i + 2] += min(L - p[i + 1], p[i + 1]);
suff[i + 1] = suff[i + 2] + L - p[i];
}
else {
suff[i + 1] = suff[i + 2] + p[i + 1] - p[i];
suff[i + 2] += min(L - p[i + 1], p[i + 1]);
}
}
pref[N] += min(p[N - 1], L - p[N - 1]);
suff[1] += min(p[0], L - p[0]);
long long mn = 1e18;
for(int i = 0; i <= N; ++i) {
//cout << pref[i] << " " << suff[i + 1] << endl;
mn = min(mn, pref[i] + suff[i + 1]);
}
return mn;
}
