#include "boxes.h"

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const int MaxN = 1e7 + 10;

long long delivery(int N, int K, int L, int p[]) {
    ll left[MaxN], right[MaxN];
    left[0] = right[0] = 0;

    int i0 = 0;
    for (; p[i0] == 0; i0++) {}
    N -= i0;
    K = min(K, N);

    for (int i = 1; i <= N; i++) {
        left[i] = 2LL * p[i - 1 + i0];
        if (i >= K) left[i] += left[i - K];
    }

    for (int i = 1; i <= N; i++) {
        right[i] = 2LL * (L - p[N - i + i0]);
        if (i >= K) right[i] += right[i - K];
    }

    ll sol = 1e18;

    for (int i = 0; i <= N; i++) {
        sol = min(sol, left[i] + right[N - i]);
        if (N - i >= K) sol = min(sol, left[i] + right[N - i - K] + L);
    }

    return sol;
}