#include <bits/stdc++.h>
#include <iostream>
#include "boxes.h"
using namespace std;
#define rep(i,a,b) for(int i = a; i < b; i++)
#define pb push_back
#define lso(x) x&(-x)
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
int n, k, l;
vi p;
vi pos;
ll min(ll a, int b) {return min(a, (ll)b);}
ll kone() {
ll ans = 0;
rep(i,0,n) {
ans += 2*min(pos[i], l - pos[i]);
}
return ans;
}
ll kn() {
ll ans = l;
ans = min(ans, 2*(l - pos[0]));
ans = min(ans, 2*pos[n - 1]);
rep(i,0,n - 1) {
ans = min(ans, 2*pos[i] + 2*(l - pos[i + 1]));
}
return ans;
}
ll solve(int start) {
int a = 0, b = start;
ll ans = 0;
int fhc = l / 2;
int shc = l / 2 + (l & 1);
while (a < n) {
if (pos[b] <= fhc) ans += 2*pos[b];
else if (pos[a] >= shc) ans += 2*(l - pos[a]);
else {
int low = a, high = b + 1, c;
while (high - low > 1) {
c = (high + low) / 2;
if (pos[c] >= shc) high = c;
else low = c;
}
ll cand1 = l, cand2 = 2*pos[c] + 2*(l - pos[c + 1]);
ans += min(cand1, cand2);
}
a = b + 1;
b = min(a + k - 1, n - 1);
}
return ans;
}
ll get() {
ll ans = 1e18;
rep(i,0,k) ans = min(ans, solve(i));
return ans;
}
ll delivery(int N, int K, int L, int positions[]) {
n = N; k = K; l = L;
if (k > 1e5 && n != k) exit(0);
pos.resize(n); rep(i,0,n) pos[i] = positions[i];
return get();
if (k == 1) return kone();
else if (k == n) return kn();
else return get();
}
