#include "boxes.h"
#include <bits/stdc++.h>
#define debug(args...) fprintf(stderr, args)
using namespace std;
const int maxn = 2e7, INF = 1e9;
int n, k, m, dp1[maxn], dp2[maxn], ini[maxn], fim[maxn], resp;
long long delivery(int N, int K, int L, int p[])
{
n = N; m = L; k = K; resp = INF;
for(int x = 0; x < n; x++)
ini[x] = 2*p[x] + ((x >= k)?ini[x-k]:0);
for(int x = n-1; x >= 0; x--)
fim[x] = 2*(m-p[x]) + ((x+k < n)?ini[x+k]:0);
for(int x = 0; x < n-1; x++)
resp = min(resp, ini[x]+fim[x+1]);
for(int x = 1; x+k < n; x++)
resp = min(resp, ini[x-1]+m+fim[x+k]);
if(k == n) resp = min(resp, m);
else resp = min(resp, min(fim[k]+m, m+ini[n-k+1]));
debug("%d\n",resp);
return resp;
}
