#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[]) {
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, L);
dist = 0;
rem = K;
}
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;
}
