#include <bits/stdc++.h>
using namespace std;
//loops (warning : long long)
#define FOR(i, l, r) for(int i = (l); i < (r); ++i)
#define ROF(i, r, l) for(int i = (r - 1); i >= l; --i)
//pairs, tuples
#define mp make_pair
#define mt make_tuple
#define ff first
#define ss second
//vectors
#define all(v) begin(v), end(v)
#define rall(v) rbegin(v), rend(v)
#define pb push_back
#define eb emplace_back
#define sum_of(v) accumulate(all(v), 0ll)
#define sz(v) (int)v.size()
#define compact(v) v.erase(unique(all(v)), end(v))
//binary search
#define lwb lower_bound
#define upb upper_bound
//other stuffs
#define dbg(x) "[" #x " = " << (x) << "]"
#define file(task) if(fopen(task".inp", "r")){ freopen(task".inp", "r", stdin); freopen(task".out", "w", stdout); }
template<typename T>
bool minimize(T& a, const T& b){
if(a > b) return a = b, true;
return false;
}
template<typename T>
bool maximize(T& a, const T& b){
if(a < b) return a = b, true;
return false;
}
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using db = double;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
using vi = vector<int>;
using vb = vector<bool>;
using vl = vector<ll>;
using vpi = vector<pi>;
using vpl = vector<pl>;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll delivery(int N, int K, int L, int p[]){
int mid = L >> 1;
sort(p, p+N);
vl pref(N+1);
FOR(i, 0, N){
int j = max(0, i - K + 1);
ll cur = (j > 0 ? pref[j-1] : 0);
if(p[j] <= mid && p[i] > mid){
cur += L;
} else if(p[j] <= mid && p[i] <= mid){
cur += p[i] * 2;
} else{
cur += (L - p[j]) * 2;
}
pref[i] = cur;
}
vl suff(N+1);
ROF(i, N, 0){
int j = min(N, i+K) - 1;
ll cur = suff[j+1];
if(p[i] <= mid && p[j] > mid){
cur += L;
} else if(p[i] <= mid && p[j] <= mid){
cur += p[j] * 2;
} else{
cur += (L - p[i]) * 2;
}
suff[i] = cur;
}
ll ans = min(pref[N-1], suff[0]);
FOR(i, 0, N-1){
minimize(ans, pref[i] + suff[i+1]);
}
return ans;
}
#ifdef LOCAL
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
freopen("in.txt", "r", stdin);
int N, K, L;
cin >> N >> K >> L;
int position[N];
FOR(i, 0, N) cin >> position[i];
cout << delivery(N, K, L, position) << '\n';
return 0;
}
#endif
