/*
0 1l 2l 3l 4
1r 2r 3r
0
1l
2l = 1
3l = 2
4 = ?
1r
2r = 1
3r = 2
[3r, 3r, 3l] -> 8
[3l, 2l, 2r] -> 8
= 16
[3r, 3r, 2r] -> 6
[3l, 3l, 2l] -> 6
1l, 2l, 3r
3l 3r 2r 2l 2l
[3l, 3r], [2l, 2l], [2r, 0l]
8 + 4 + 4 = 12
[3r, 2r], [3l, 2l], [2l, 0l]
6 + 6 + 4 = 16
10 2 10
4 3 0 1 1 2 0 5 1 6
1 1 1 2 3 4
5 6
10 7 10
7 8 1 4 3 8 7 0 4 6
4 3 10
4 9 2 9
2 4
9 9
FAILING TEST CASE:
5 3 10
2 5 8 4 3
2 3 4
5 8
2 3 4 5
8
??? Does this fail?
10 7 10
7 8 1 4 3 8 7 0 4 6
0 1 3 4
6 7 7 8 8
*/
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pi;
typedef pair<ll, ll> pll;
typedef vector<pi> vpi;
typedef vector<pll> vpll;
#define first fi;
#define second se;
ll delivery(int intn, int intk, int intl, int pos_int[]) {
ll n = intn, k = intk, l = intl;
vll pos(n, 0ll);
for(ll i = 0; i < n; i++) {
pos[i] = pos_int[i];
}
sort(pos.begin(), pos.end());
vll pref(n + 1, 0ll);
vll suff(n + 1, 0ll);
for(ll i = 1ll; i < n + 1; i++) {
pref[i] = (i >= k ? pref[i - k] : 0ll) + pos[i - 1];
}
for(ll i = n - 1; i >= 0ll; i--) {
suff[i] = (i + k <= n ? suff[i + k] : 0ll) + l - pos[i];
}
ll ans = numeric_limits<ll>::max();
for(ll i = 0; i <= n; i++) {
ans = min(ans, (pref[i] + suff[i]) << 1ll);
if(i + k <= n) ans = min(ans, ((pref[i] + suff[i + k]) << 1ll) + l);
}
return ans;
}
#ifdef DEBUG
int main() {
cin.tie(nullptr);
cout.tie(nullptr);
ios_base::sync_with_stdio(false);
int n, k, l;
cin >> n >> k >> l;
vi positions(n, 0);
for(int& pos : positions) {
cin >> pos;
}
cout << delivery(n, k, l, &positions[0]) << endl;
}
#endif
