// clang-format off
#include "boxes.h"
#include <bits/stdc++.h>
using i64 = int64_t;
template <typename T = int> T scan() {
T ret; std::cin >> ret;
return ret;
}
long long solve(const int N, const int K, const int L, std::vector<int> P) {
std::vector<i64> l_sum(N + 1), r_sum(N + 1);
l_sum[0] = r_sum[N] = 0;
for (int i = 0; i < K; ++i) {
l_sum[i + 1] = std::min({L, 2 * (L - P[0]), 2 * P[i]});
}
for (int i = N; i > N - K; --i) {
r_sum[i - 1] = std::min({L, 2 * P[N - 1], 2 * (L - P[i - 1])});
}
for (int i = K; i < N; ++i) {
const int cost = std::min({L, 2 * P[i], 2 * (L - P[i - K + 1])});
l_sum[i + 1] = l_sum[i - K + 1] + cost;
}
for (int i = N - K; i > 0; --i) {
const int cost = std::min({L, 2 * (L - P[i - 1]), 2 * P[i + K - 2]});
r_sum[i - 1] = r_sum[i + K - 1] + cost;
}
i64 answer = (i64)5000000000000000;
for (int i = 0; i <= N; ++i) {
answer = std::min(answer, l_sum[i] + r_sum[i]);
}
return answer;
}
long long delivery(int N, int K, int L, int P[]) {
std::vector<int> vec(N);
for (int i = 0; i < N; ++i) vec[i] = P[i];
return solve(N, K, L, vec);
}
