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