#include "boxes.h"
#include <bits/stdc++.h>
// #include <ext/rope>
// #include <ext/pb_ds/assoc_container.hpp>
// using namespace __gnu_pbds;
// using namespace __gnu_cxx;
using namespace std;
// #define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define ll long long
#define ull unsigned long long
#define ld long double
#define pb push_back
#define bit(mask, i) ((mask >> i) & 1)
#define el '\n'
#define F first
#define S second
template <class X, class Y> bool maximize(X &x, const Y &y) { return (x < y ? x = y, 1 : 0); }
template <class X, class Y> bool minimize(X &x, const Y &y) { return (x > y ? x = y, 1 : 0); }
const int INF = 1e9;
const ll LINF = 1e18;
const int MOD = 1e9 + 7;
const int MULTI = 0;
const ld eps = 1e-9;
const int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0}; // R D L U
const int ddx[4] = {-1, 1, 1, -1}, ddy[4] = {1, 1, -1, -1}; // UR DR DL UL
const char cx[4] = {'R', 'D', 'L', 'U'};
const ll base = 31;
const int nMOD = 2;
const ll mods[] = {(ll)1e9 + 10777, (ll)1e9 + 19777, (ll)1e9 + 3, (ll)1e9 + 3777};
const int maxn = 1e7 + 5;
ll dp[maxn], dp1[maxn];
ll delivery(int N, int K, int L, int p[]) {
for (int i = 1; i <= N; ++i)
if (i >= K)
dp[i] = dp[i - K] + 2LL * p[i - 1];
else
dp[i] = 2LL * p[i - 1];
for (int i = 1; i <= N; ++i)
if (i >= K)
dp1[i] = dp1[i - K] + 2LL * (L - p[N - i]);
else
dp1[i] = 2LL * (L - p[N - i]);
ll res = dp[N];
for (int i = 0; i <= N; ++i) {
minimize(res, dp[i] + dp1[N - i]);
if (N - i >= K) minimize(res, dp[i] + dp1[N - i - K] + L);
}
return res;
}
