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

using namespace std;

namespace {

typedef long long ll;

const int N = 1e6 + 7;

int n, k, l, p[N];
ll dp[N];

}

long long delivery(int grdn, int grdk, int grdl, int grdp[]) {
	n = grdn;
	k = grdk;
	l = grdl;
	for (int i = 0; i < n; ++i) {
		p[i] = grdp[i];
	}
	memset(dp, 0x3f, (n + 1) * sizeof dp[0]);
	dp[0] = 0;
	for (int i = 0; i < n; ++i) {
		for (int j = i; j < min(i + k, n); ++j) {
			int cost = min({2 * p[j], 2 * (l - p[i]), l});
			dp[j + 1] = min(dp[j + 1], dp[i] + cost);
		}
	}
	return dp[n];
}