#include<bits/stdc++.h>
#include "boxes.h"
using namespace std;
const int MAXN = 10000010;
const int INF = 2e9 + 7;
int N, K, L, POSITIONS[MAXN], pos[MAXN];
long long int clk[MAXN], cnt[MAXN];
long long int delivery(int n, int k, int l, int positions[])
{
for(int i = 0; i < n; i++) pos[i + 1] = positions[i];
sort(pos, pos + n + 1);
for(int i = 1; i <= n; i++)
{
cnt[i] = 2 * pos[i];
if(i - k > 0) cnt[i] += cnt[i - 1];
}
for(int i = n; i > 0; i--)
{
clk[i] = 2 * (l - pos[i]);
if(i + k <= n) clk[i] += clk[i + k];
}
long long int ans = INF;
for(int i = 0; i <= n; i++)
ans = min(ans, cnt[i] + clk[i + 1]);
for(int i = 0; i + k + 1 <= n + 1; i++)
ans = min(ans, cnt[i] + l + clk[i + k + 1]);
for(int i = n + 1; i - k - 1 >= 0; i--)
ans = min(ans, clk[i] + l + cnt[i - k - 1]);
return ans;
}
/*
int main ()
{
scanf("%d %d %d", &N ,&K, &L);
for(int i = 0; i < N; i++) scanf("%d", &POSITIONS[i]);
printf("%lld\n",delivery(N, K, L, POSITIONS));
}
*/
/*
4 2 8
1 2 3 5
*/
