#include <bits/stdc++.h>
using namespace std;
using ll = long long;
long long delivery(int N, int K, int L, int p[]) {
vector<int> prefix(N), suffix(N);
for (int i = 0; i < N; ++i) {
prefix[i] = p[i] + min(p[i],L - p[i]);
suffix[N - i - 1] = L - p[i] + min(p[i], L - p[i]);
}
ll best = 1e18;
for (int i = 0; i <= N; ++i) {
//Till I is left
ll ans = 0;
ll t = i - 1;
ll j = -1;
while (j < t) {
ll jump = t - j;
if (jump > K) jump = K;
if (jump == 0) break;
j += jump;
ans += prefix[j];
}
j = -1;
t = N - i - 1;
while (j < t) {
ll jump = t - j;
if (jump > K) jump = K;
if (jump == 0) break;
j += jump;
ans += suffix[j];
}
best = min(best, ans);
}
return best;
}
#if DEBUG
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;
}
int main() {
int N, K, L, i; cin >> N >> K >> L;
int *p = (int*)malloc(sizeof(int) * (unsigned int)N);
for (i = 0; i < N; i++) {
cin >> p[i];
}
cout << delivery(N, K, L, p);
return 0;
}
#endif
