#include "boxes.h"
#include <bits/stdc++.h>
using namespace std;
long long cwtour[1000100], cwwtour[1000100];
long long delivery(int N, int K, int L, int p[]) {
for (int i = 0; i < N; i++) {
if (i < K) cwtour[i] = p[i];
else cwtour[i] = cwtour[i - K] + p[i];
}
for (int i = N - 1; i >= 0; i--) {
if (i >= N - K) cwwtour[i] = L - p[i];
else cwwtour[i] = cwwtour[i + K] + L - p[i];
}
long long ans = min(2 * cwtour[N - 1], 2 * cwwtour[0]);
for (int i = 1; i < N; i++) ans = min(ans, 2 * cwtour[i - 1] + 2 * cwwtour[i]);
if (K < N) {
ans = min(ans, L + 2 * cwwtour[K]);
ans = min(ans, L + 2 * cwtour[N - K - 1]);
for (int i = 1; i + K < N; i++) ans = min(ans, 2 * cwtour[i - 1] + L + 2 * cwwtour[i + K]);
} else {
ans = min(ans, (long long) L);
}
return ans;
}
