#include "boxes.h"
#include <bits/stdc++.h>
using namespace std;
long long delivery(int n, int k, int l, int p[]) {
vector<long long> j(n+1);
for(int i = 1; i <= n; i++){
j[i] = p[i-1];
}
vector<long long> pref(n+1);
long long ans = 1e18;
for(int i = 1; i <= n; i++){
if(i <= k){
pref[i] = j[i] + min(l - j[i], j[i]);
}else{
pref[i] = pref[i-k] + (j[i] - j[i-k]) + j[i-k] * 2 + min(j[i], l-j[i]);
}
}
vector<long long> suf(n+2);
for(int i = n; i >= 1; i--){
if(i > n-k){
suf[i] = l - j[i] + min(j[i], l-j[i]);
}else{
suf[i] = suf[i+k] + (j[i+k] - j[i]) + (l - j[i+k]) * 2 + min(j[i], l-j[i]);
}
}
for(int i = 0; i <= n; i++){
// cout << pref[i] << " " << suf[i+1] << " " << i << endl;
ans = min(pref[i] + suf[i+1], ans);
}
return ans;
}
