#include "boxes.h"
#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
typedef long long ll;
using namespace std;
//using namespace __gnu_pbds;
#define FOR(i, x, y) for(ll i=x; i<y; i++)
#define FORNEG(i, x, y) for(ll i=x; i>y; i--)
//#define ordered_set tree<ll, null_type,less_equal<ll>, rb_tree_tag,tree_order_statistics_node_update>
#define fast() ios_base::sync_with_stdio(false);cin.tie(NULL)
ll dp1[10000001], dp2[10000001];
long long delivery(int N, int K, int L, int p[]) {
FOR(i,0,K){
dp1[i] = p[i]*2;
}
FOR(i,K,N){
dp1[i] = dp1[i-K] + p[i]*2;
}
FORNEG(i,N-1, N-K-1){
dp2[i] = (L-p[i])*2;
}
FORNEG(i, N-K-1, -1){
dp2[i] = dp2[i+K] + (L-p[i])*2;
}
ll ans = dp2[0];
FOR(i,0,N){
ans = min(ans, dp1[i] + dp2[i+1]);
}
return ans;
}
