#include "boxes.h"
#include <bits/stdc++.h>

typedef long long ll;
const int N = (int)1e7 + 2;
int n, k, l;
ll dp[N], pd[N];
ll delivery(int nn, int kk, int LL, int p[]) {
    n = nn;k = kk;l = LL;

    for(int i = 0; i < n; i++) {
        ll pr = (i - k >= 0 ? dp[i - k] : 0);
        dp[i] = pr + p[i] + p[i];
    }
    ll res = dp[n - 1];
    for(int i = 0; i < n; i++) {
        p[i] = l - p[i];
    }
    for(int i = n - 1; i >= 0; i--) {
        ll pr = (i + k <= n - 1 ? pd[i + k] : 0);
        pd[i] = pr + p[i] + p[i];
    }

    for(int i = 0; i < n - 1; i++) {
        res = std::min(res, dp[i] + pd[i + 1]);
    }
    return res;
}