#include <bits/stdc++.h>
#include "boxes.h"
using namespace std;
/*
static char _buffer[1024];
static int _currentChar = 0;
static int _charsNumber = 0;
static FILE *_inputFile, *_outputFile;
static inline int _read() {
if (_charsNumber < 0) {
exit(1);
}
if (!_charsNumber || _currentChar == _charsNumber) {
_charsNumber = (int)fread(_buffer, sizeof(_buffer[0]), sizeof(_buffer), _inputFile);
_currentChar = 0;
}
if (_charsNumber <= 0) {
return -1;
}
return _buffer[_currentChar++];
}
static inline int _readInt() {
int c, x, s;
c = _read();
while (c <= 32) c = _read();
x = 0;
s = 1;
if (c == '-') {
s = -1;
c = _read();
}
while (c > 32) {
x *= 10;
x += c - '0';
c = _read();
}
if (s < 0) x = -x;
return x;
}
*/
const int64_t INF = 1e18L;
void minSelf(int64_t &x, int64_t y) {
if (y < x) {
x = y;
}
}
long long delivery(int n, int k, int L, int p[]) {
vector<int64_t> l(n + 1), r(n + 2);
/// l[i] =def= costul minim sa livrez 1..i mergand doar la dreapta cand livrez si intorcandu-ma la inceput in ce directie vreau
/// Analog r[i] in sens invers
for (int i = 1; i <= n; ++i) {
int last = max(0, i - k);
l[i] = l[last] + p[i - 1] + min(p[i - 1], L - p[i - 1]);
}
for (int i = n; i > 0; --i) {
int nxt = min(n + 1, i + k);
r[i] = r[nxt] + (L - p[i - 1]) + min(p[i - 1], L - p[i - 1]);
}
int64_t best = INF;
for (int i = 0; i <= n; ++i) {
minSelf(best, l[i] + r[i + 1]);
}
/// Observatie: Va fi maxim o tura de impartit cadouri in care parcurg cercul complet si aia va fi
/// ultima, in care voi imparti toate cadourile ramase, asa ca fixez si variantele in care am k
/// cadouri ramase si la final si parcurg tot cercul
for (int i = 0; i <= n - k; ++i) {
minSelf(best, l[i] + r[i + k + 1] + L);
}
return best;
}
/*
int main() {
_inputFile = fopen("boxes.in", "rb");
_outputFile = fopen("boxes.out", "w");
int N, K, L, i;
N = _readInt();
K = _readInt();
L = _readInt();
int *p = (int*)malloc(sizeof(int) * (unsigned int)N);
for (i = 0; i < N; i++) {
p[i] = _readInt();
}
fprintf(_outputFile, "%lld\n", delivery(N, K, L, p));
return 0;
}
*/
