//#define local
#ifndef local
#include "boxes.h"
#endif
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define ll long long
#define fi first
#define se second
#define pb push_back
#define mp make_pair
typedef pair<ll, ll> ii;
typedef pair<ii, ll> iii;
typedef pair<ii, ii> iiii;
const ll N = 1e7 + 5;
const ll oo = 1e18 + 7, mod = 1e9 + 7;
mt19937 rng(1);
ll rnd(ll l, ll r){
ll temp = rng() % (r - l + 1);
return abs(temp) + l;
}
ll cnt;
ll le[N], ri[N];
ll tol1[N], tol2[N];
ll n, k, l;
ll positions[N];
ll pref[N], suff[N];
ll delivery(int N, int K, int L, int positionss[]){
for(int i = 0; i < N; i++) positions[i] = positionss[i];
n = N, k = K, l = L;
for(ll i = 0; i < n; i++) cnt += (positions[i] <= (l/2));
//cout << cnt << "\n";
for(ll i = 0; i < cnt; i++){
tol1[i] = (i >= k ? tol1[i - k] : 0) + positions[i] * 2;
}
for(ll i = 0; i <= k; i++) pref[i] = suff[i] = oo;
for(ll i = 0; i < (n - cnt); i++){
tol2[i] = (i >= k ? tol2[i - k] : 0) + (l - positions[n - 1 - i]) * 2;
pref[(n - cnt - 1 - i) % k] = min(pref[(n - cnt - 1 - i) % k], tol2[i] + (((n - cnt - 1 - i) + (k - 1)) / k) * l);
suff[(n - cnt - 1 - i) % k] = min(suff[(n - cnt - 1 - i) % k], tol2[i] + (((n - cnt - 1 - i) + (k - 1)) / k) * l);
}
pref[(n - cnt) % k] = min(pref[(n - cnt) % k], ((n - cnt + (k - 1)) / k) * l);
suff[(n - cnt) % k] = min(suff[(n - cnt) % k], ((n - cnt + (k - 1)) / k) * l);
for(ll i = 2; i < k; i++) pref[i] = min(pref[i], pref[i - 1]);
//cout << pref[k - 1] << "\n";
for(ll i = k - 2; i >= 1; i--) suff[i] = min(suff[i], suff[i + 1]);
ll answer = oo;
//cout << tol1[cnt - 1] << " " << tol2[n - cnt - 1] << "\n";
for(ll i = -1; i < cnt; i++){
ll temp1 = (i >= 0 ? tol1[i] : 0);
temp1 += ((cnt - 1 - i + (k - 1)) / k) * l;
// cout << temp1 << " " << pref[0] << "\n";
ll md = (cnt - 1 - i) % k;
if(md){
answer = min(answer, temp1 + pref[k - md] - l);
answer = min(answer, temp1 + suff[k - md + 1]);
answer = min(answer, temp1 + pref[0]);
}
else{
answer = min(answer, temp1 + pref[k - 1]);
answer = min(answer, temp1 + pref[0]);
}
}
return answer;
/*
for(ll i = -1; i < cnt; i++){
for(ll j = -1; j < (n - cnt); j++){
ll temp1 = (i >= 0 ? tol1[i] : 0);
ll temp2 = (j >= 0 ? tol2[j] : 0);
answer = min(answer, temp1 + temp2 + ((n - 2 - i - j + (k - 1)) / k) * l);
// cout << i << " " << j << " " << tol1[i] << " " << tol2[j] << "\n";
}
}*/
return answer;
}
#ifdef local
void process(){
int n, k, l;
cin >> n >> k >> l;
int arr[n];
for(ll i = 0; i < n; i++) cin >> arr[i];
cout << delivery(n, k, l, arr) << "\n";
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
// freopen("boxes.inp", "r", stdin);
ll t = 1;
//cin >> t;
while(t--) process();
}
#endif
