#include <bits/stdc++.h>
//#include "grader.cpp"
#include "boxes.h"
using namespace std;
#define ll long long
#define pb push_back
#define mk make_pair
#define fr first
#define sc second
#define vi vector < int >
#define vl vector < ll >
#define pi pair < int, int >
#define pii pair < int, pi >
#define vii vector < pi >
const int MAXN = 1e7 + 7;
const ll INF = 1e18 + 7;
ll pr[MAXN], sf[MAXN];
ll ans;
long long delivery(int N, int K, int L, int p[]) {
for (int i = 0; i < N; i++){
pr[i] = pr[i - 1] + p[i] + min(p[i], L - p[i]);
if ((i + 1) % K != 1 && K != 1)
pr[i] -= (p[i - 1] + min(p[i - 1], L - p[i - 1]));
}
for (int i = N - 1; i >= 0; i--){
sf[i] = sf[i + 1] + L - p[i] + min(p[i], L - p[i]);
if ((N - i) % K != 1 && K != 1)
sf[i] -= (L - p[i + 1] + min(p[i + 1], L - p[i + 1]));
}
ans = sf[0];
for (int i = 0; i < N; i++)
ans = min(ans, pr[i] + sf[i + 1]);
return ans;
}
