#include "boxes.h"
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <queue>
#include <cassert>
using namespace std;
#define rep(i, n) for (int i=0; i<(n); i++)
#define all(x) x.begin(), x.end()
#define uniq(x) x.erase(unique(all(x)), x.end())
#define index(x, y) (int)(lower_bound(all(x), y) - x.begin())
#define pb push_back
#define _1 first
#define _2 second
#define INF (1LL<<60)
typedef pair<int, int> P;
long long delivery(int N, int K, int L, int X[]) {
//rep(i, N) cout << X[i]<<",";cout<<"\n";
long long m = INF;
rep(i, N+1) {
long long s = 0;
for (int x=i-1; x>=0; x-=K) s += min(2LL*X[x], (long long)L);
for (int x=i; x<N; x+=K) s += min(2LL*(L-X[x]), (long long)L);
m = min(m, s);
}
return m;
}
