#include "boxes.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int start;
ll ans, pf[1000005], sf[1000005];
ll delivery(int N, int K, int L, int p[]) {
start = N;
for (int i = 0; i < N; i++)
pf[i] = (i - K >= 0 ? pf[i - K] : 0ll) + 2ll * (ll)p[i];
for (int i = N - 1; i >= 0; i--)
sf[i] = (i + K < N ? sf[i + K] : 0ll) + 2ll * (ll)(L - p[i]);
for (int i = 0; i < N; i++) {
if ((ll)L + (i > 0 ? pf[i - 1] : 0ll) < (ll)pf[min(N - 1, i + K - 1)]) {
start = i;
break;
}
}
ans = LLONG_MAX;
for (int i = 0; i <= N; i++) ans = min(ans, (ll)(i ? pf[i - 1] : 0) + (ll)sf[i]);
for (int i = start; i <= N; i += K)
ans = min(ans, (start > 0 ? pf[start - 1] : 0ll) + sf[i] + (ll)(i - start) / (ll)K * (ll)L);
return ans;
}
