#ifndef LOCAL
#include "boxes.h"
#endif
#include <vector>
#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
template <class T>
using Vec = std::vector<T>;
constexpr long long INF = std::numeric_limits<long long>::max();
long long delivery(int N, int K, int Len, int P[]) {
Vec<int> left, right;
left.reserve(N);
right.reserve(N);
for (int i = 0; i < N; ++i) {
const auto l = P[i];
const auto r = Len - P[i];
if (l <= r) {
left.push_back(l);
}
else {
right.push_back(r);
}
}
std::reverse(right.begin(), right.end());
const int L = (int) left.size();
const int R = (int) right.size();
Vec<long long> memo(K);
for (int i = 0; i < R; ++i) {
memo[i % K] += std::min(Len, 2 * right[i]);
}
Vec<long long> sum(K);
long long ret = INF;
for (int i = 0; i <= L; ++i) {
const auto over = ((L - i) + (K - 1)) / K;
const auto remain = (N - i) - K * over;
ret = std::min(ret, (i == 0 ? 0 : sum[(i - 1) % K]) + (long long) Len * over + (remain <= 0 ? 0 : memo[(remain - 1) % K]));
if (i != L) {
sum[i % K] += 2 * left[i];
}
}
return ret;
}
#ifdef LOCAL
int main() {
int N, K, L;
std::cin >> N >> K >> L;
int P[100] = {};
for (int i = 0; i < N; ++i) {
std::cin >> P[i];
}
std::cout << delivery(N, K, L, P) << '\n';
return 0;
}
#endif
