#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define replr(i, a, b) for (int i = int(a); i <= int(b); ++i)
#define reprl(i, a, b) for (int i = int(a); i >= int(b); --i)
#define rep(i, n) for (int i = 0; i < int(n); ++i)
#define mkp(a, b) make_pair(a, b)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<VPI> VVPI;
typedef pair<ll, ll> PLL;
typedef vector<ll> VL;
typedef vector<PLL> VPL;
typedef vector<VL> VVL;
typedef vector<VVL> VVVL;
typedef vector<VPL> VVPL;
template<class T> T setmax(T& a, T b) {if (a < b) return a = b; return a;}
template<class T> T setmin(T& a, T b) {if (a < b) return a; return a = b;}
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template<typename T>
using indset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#include "boxes.h"
int n, k;
ll l;
ll delivery(int N_ARG, int K_ARG, int L_ARG, int POS_ARG[]) {
/*ll realanswer = TEST123::delivery(N_ARG, K_ARG, L_ARG, POS_ARG);*/
n = N_ARG;
k = K_ARG;
l = L_ARG;
VL pos;
pos.pb(0);
rep(i, n) pos.pb(POS_ARG[i]);
pos.pb(l);
n += 2;
/*return realanswer;*/
VL f(n);
replr(i, 0, n-1) {
for (int c = i; c >= 0; c -= k) {
f[i] += 2*pos[c];
}
}
VL g(n);
replr(j, 0, n-1) {
for (int c = j; c < n; c += k) {
g[j] += 2*(l-pos[c]);
}
}
auto func = [&](int i, int j) {
return (j-i-1 + k-1) / k * l + g[j] + f[i];
};
ll ans = 1e18;
replr(i, 0, n-2) {
int j = min(n-1, i+k+1);
/*replr(j, i+1, n-1) {*/
setmin(ans, func(i, j));
/* if (func(i, j) == 10) cout << i << ", " << j << endl;*/
/*}*/
}
return ans;
}
