/*
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
*/
#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;
vll facts = {1ll, 1ll, 2ll, 6ll, 24ll, 120ll, 720ll, 5040ll, 40320ll, 362880ll, 3628800ll};
ll solve_kn(ll n, ll l, const vll& pos) {
if(n == 0ll) return 0ll;
ll max_left = 0ll;
ll max_right = l;
for(ll i = 0; i < n; i++) {
if(pos[i] > (l >> 1ll) || ((l & 1) == 0ll && pos[i] == (l >> 1ll))) max_right = min(max_right, pos[i]);
if(l - pos[i] > (l >> 1ll)) max_left = max(max_left, pos[i]);
}
return min(l, (l - max_right + max_left) << 1ll);
}
ll delivery(int intn, int intk, int intl, int pos_int[]) {
ll n = intn, k = intk, l = intl;
vll posl;
vll posr;
for(ll i = 0; i < n; i++) {
if(pos_int[i] > (l >> 1ll)) posr.push_back(pos_int[i]);
else posl.push_back(pos_int[i]);
}
ll ans = numeric_limits<ll>::max(), cost = 0ll;
ll num_groups = (n - 1ll) / k + 1ll;
sort(posl.begin(), posl.end());
sort(posr.begin(), posr.end(), greater<ll>());
for(ll orientation = 0ll; orientation < 2ll; orientation++) {
for(ll num_circ = 0ll; num_circ <= num_groups; num_circ++) {
cost = 0ll;
ll lp = posl.size() - 1ll, rp = posr.size() - 1ll;
for(ll i = 0ll; i < num_circ; i++) {
vll group;
for(ll j = 0ll; j < k && (lp >= 0ll || rp >= 0ll); j++) {
if(lp >= 0ll && rp >= 0ll){
if(posl[lp] > l - posr[rp] || (orientation == 0ll && posl[lp] == l - posr[rp])) {
group.push_back(posl[lp]);
lp--;
} else {
group.push_back(posr[rp]);
rp--;
}
} else if(lp >= 0ll) {
group.push_back(posl[lp]);
lp--;
} else {
group.push_back(posr[rp]);
rp--;
}
}
cost += solve_kn(group.size(), l, group);
}
vll group;
while(lp >= 0ll) {
group.push_back(posl[lp]);
lp--;
if((ll)group.size() == k) {
cost += solve_kn(group.size(), l, group);
group.clear();
}
}
cost += solve_kn(group.size(), l, group);
group.clear();
while(rp >= 0ll) {
group.push_back(posr[rp]);
rp--;
if((ll)group.size() == k) {
cost += solve_kn(group.size(), l, group);
group.clear();
}
}
cost += solve_kn(group.size(), l, group);
ans = min(ans, cost);
}
}
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
