#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
#define fi first
#define se second
#define left BAO
#define right ANH
#define pb push_back
#define pf push_front
#define mp make_pair
#define ins insert
#define btpc __builtin_popcount
#define btclz __builtin_clz
#define sz(x) (int)(x.size());
#define all(x) x.begin(), x.end()
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};
template<class X, class Y>
bool minimize(X &x, const Y &y) {
if (x > y)
{
x = y;
return true;
}
return false;
}
template<class X, class Y>
bool maximize(X &x, const Y &y) {
if (x < y)
{
x = y;
return true;
}
return false;
}
const int MOD = 1e9 + 7; //998244353
template<class X, class Y>
void add(X &x, const Y &y) {
x = (x + y);
if(x >= MOD) x -= MOD;
}
template<class X, class Y>
void sub(X &x, const Y &y) {
x = (x - y);
if(x < 0) x += MOD;
}
/* Author : Le Ngoc Bao Anh, 12A5, LQD High School for Gifted Student*/
const ll INF = 1e9;
const int N = 1e7 + 10;
ll pref[N], suff[N];
int a[N];
ll delivery(int n, int k, int l, int positions[]) {
for(int i = 0; i < n; i++) a[i + 1] = positions[i];
for(int i = 1; i <= n; i++) {
pref[i] = pref[max(0, i - k)] + a[i] * 2;
}
for(int i = n; i >= 1; i--) {
suff[i] = suff[min(n + 1, i + k)] + (l - a[i]) * 2;
}
ll ans = min(pref[n], suff[1]);
for(int i = 1; i < n; i++) {
minimize(ans, pref[i] + suff[i + 1]);
}
for(int i = 1; i + k - 1 <= n; i++) {
minimize(ans, pref[i - 1] + l + suff[i + k]);
}
return ans;
}
