#include "boxes.h"
#include <stdio.h>
#include <iostream>
#include <string>
#include <set>
#include <map>
#include <cstring>
#include <unordered_map>
#include <vector>
#include <fstream>
#include <bitset>
#include <tuple>
#include <cmath>
#include <cstdint>
#include <stack>
#include <cassert>
#include <cstdio>
#include <queue>
#include <iterator>
#include <iomanip>
#include <algorithm>
#include <sstream>
using namespace std;
long long delivery(int N, int K, int L, int p[]) {
#define int long long
long long sum = 0;
if (K == 1) {
for (int i = 0; i < N; i++)
{
sum += min(p[i], L - p[i]) * 2;
}
}
else {
int dist = 0;
bool ldir = true;
int rem = K;
int c = 0;
for (c = 0; c < N; c++)
{
if (rem == 0) {
sum += min(dist * 2, (long long)L);
dist = 0;
rem = K;
if (dist > L / 2) {
ldir = false;
break;
}
}
if (min(L, p[c] * 2) >= (dist + (L - p[c])) * 2) {
ldir = false;
sum += dist * 2;
break;
}
else dist = p[c];
rem--;
}
if (ldir) sum += min(L, p[N - 1] * 2);
else {
while (c < N) {
sum += (L - p[c]) * 2;
c += K;
}
}
}
return sum;
}
