#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
#define pb push_back
#define f first
#define s second
namespace debug {
const int DEBUG = true;
template<class T1, class T2>
void pr(const pair<T1, T2> &x);
template<class T, size_t SZ>
void pr(const array<T, SZ> &x);
template<class T>
void pr(const vector<T> &x);
template<class T>
void pr(const set<T> &x);
template<class T1, class T2>
void pr(const map<T1, T2> &x);
template<class T>
void pr(const T &x) { if (DEBUG) cout << x; }
template<class T, class... Ts>
void pr(const T &first, const Ts &... rest) { pr(first), pr(rest...); }
template<class T1, class T2>
void pr(const pair<T1, T2> &x) { pr("{", x.f, ", ", x.s, "}"); }
template<class T>
void prIn(const T &x) {
pr("{");
bool fst = 1;
for (auto &a : x) {
pr(fst ? "" : ", ", a), fst = 0;
}
pr("}");
}
template<class T, size_t SZ>
void pr(const array<T, SZ> &x) { prIn(x); }
template<class T>
void pr(const vector<T> &x) { prIn(x); }
template<class T>
void pr(const set<T> &x) { prIn(x); }
template<class T1, class T2>
void pr(const map<T1, T2> &x) { prIn(x); }
void ps() { pr("\n"), cout << flush; }
template<class Arg, class... Args>
void ps(const Arg &first, const Args &... rest) {
pr(first, " ");
ps(rest...);
}
}
using namespace debug;
ll delivery(int N, int K, int L, int posI[]) {
vi pos(posI, posI + N);
pos.insert(pos.begin(), 0);
pos.pb(0);
vl costR(N + 1);
costR[0] = 0;
for (int i = 1; i <= N; i++) {
costR[i] = 2ll * pos[i] + costR[max(0, i - K)];
}
vl costL(N + 2);
costL[N + 1] = 0;
for (int i = N; i >= 1; i--) {
costL[i] = 2ll * (L - pos[i]) + costL[min(N + 1, i + K)];
}
ll ans = 1e15;
// no full circles
for (int i = 0; i <= N; i++) {
ans = min(ans, costR[i] + costL[i + 1]);
}
// one full circle
for (int i = 0; i <= N; i++) {
ans = min(ans, L + costR[i] + costL[min(N + 1, i + K + 1)]);
}
return ans;
}
