#include <bits/stdc++.h>
#include "boxes.h"
using namespace std;
const int maxn = 1e7+10;
typedef long long ll;
int p[maxn];
ll pref[maxn], suf[maxn];
long long delivery(int N, int K, int L, int positions[])
{
int n = N, k = K;
for (int i = 1; i <= n; i++)
p[i] = positions[i-1];
int mid = L/2;
int last_p = 0, last_s = n+1;
if (p[1] <= mid) pref[1] = 2ll*(ll)p[1], last_p = 1;
for (int i = 2; i <= n; i++)
{
if (p[i] > mid) break;
pref[i] = 2ll*(ll)p[i] + pref[max(0, i-k)];
last_p = i;
}
if (p[n] > mid) suf[n] = 2ll*((ll)L-(ll)p[n]), last_s = n;
for (int i = n-1; i >= 1; i--)
{
if (p[i] <= mid) break;
suf[i] = 2ll*((ll)L-(ll)p[i]) + suf[min(n+1, i+k)];
last_s = i;
}
ll ans = pref[last_p] + suf[last_s];
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= k; j++)
{
if (!last_p && last_s > n) break;
if (!last_p) last_s++;
else if (last_s > n) last_p--;
else if (p[last_p] > L-p[last_s]) last_p--;
else last_s++;
}
ans = min(ans, 1ll*(ll)i*(ll)L + pref[last_p] + suf[last_s]);
}
return ans;
}
