#include <bits/stdc++.h>
#include "boxes.h"
using namespace std;
using ll = long long;
using pii = pair<int, int>;
const int mxN = 1e6+5;
ll memo[mxN][2];
vector<int> pos;
int L, k, n;
ll solve(int i, int t) {
if (i >= pos.size()) return 0;
if (memo[i][t] != -1) return memo[i][t];
ll result=1e18;
int md = n%k;
//Va a quedar un bloque de tamaño md;
//Caso bloque de k
if (i+k <= n) {
int s = k;
int l = pos[i];
int r = pos[i+s-1];
ll cost = min(2*min(r, L-l), L);
result = min(result, cost + solve(i+s, t));
}
//Caso bloque de md
if (t==0 && i+md <= n && n%k != 0) {
int s = md;
int l = pos[i];
int r = pos[i+s-1];
ll cost = min(2*min(r, L-l), L);
result = min(result, cost + solve(i+s, 1));
}
memo[i][t] = result;
return memo[i][t];
}
ll delivery(int N, int K, int l, int* a) {
n = N;
k = K;
L = l;
pos.assign(n, 0);
for (int i=0; i<n; i++) {
pos[i] = a[i];
}
memset(memo, -1, sizeof(memo));
return solve(0, 0);
}
