#include<bits/stdc++.h>
using namespace std;
#define inf 0x3f3f3f3f
#define sz(x) int((x).size())
#define fi first
#define se second
typedef long long ll;
typedef pair<int, int> ii;
template<class X, class Y>
inline bool maximize(X &x, const Y &y) {return (x < y ? x = y, 1 : 0);}
template<class X, class Y>
inline bool minimize(X &x, const Y &y) {return (x > y ? x = y, 1 : 0);}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int Random(int l, int r) {
return uniform_int_distribution<int>(l, r)(rng);
}
const int MAXN = 1e7+7;
ll dpL[MAXN], dpR[MAXN];
int a[MAXN], nArr, k, L;
#ifdef Nhoksocqt1
ll delivery(int _N, int _K, int _L, int _pos[]);
int _P[MAXN];
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
freopen("BOXES.inp", "r", stdin);
freopen("BOXES.out", "w", stdout);
int N, K, L;
cin >> N >> K >> L;
//N = Random(1, 10), K = Random(1, N), L = Random(1, 1e9); cout << N << ' ' << K << ' ' << L << '\n';
for (int i = 0; i < N; ++i)
cin >> _P[i];
//for (int i = 0; i < N; ++i) _P[i] = Random(0, L - 1); sort(_P, _P + N); for (int i = 0; i < N; ++i) cout << _P[i] << " \n"[i + 1 == N];
cout << delivery(N, K, L, _P) << '\n';
return 0;
}
#endif // Nhoksocqt1
ll delivery(int _N, int _K, int _L, int _pos[]) {
nArr = _N, k = _K, L = _L;
int cnt0(0);
while(cnt0 < nArr && _pos[cnt0] == 0)
++cnt0;
for (int i = cnt0 + 1; i <= nArr; ++i)
a[i - cnt0] = _pos[i - 1];
nArr = _N - cnt0;
for (int i = 0; i <= nArr + 1; ++i)
dpL[i] = dpR[i] = 1e18;
dpL[0] = dpR[nArr + 1] = 0;
deque<int> dq;
dq.push_back(0);
for (int i = 1; i <= nArr; ++i) {
dpL[i] = dpL[dq.front()] + min(L, 2 * a[i]);
while(dq.size() && dpL[dq.back()] >= dpL[i])
dq.pop_back();
dq.push_back(i);
if(dq.front() + k <= i)
dq.pop_front();
}
while(dq.size())
dq.pop_back();
dq.push_back(nArr + 1);
for (int i = nArr; i > 0; --i) {
dpR[i] = dpR[dq.front()] + min(L, 2 * (L - a[i]));
while(dq.size() && dpR[dq.back()] >= dpR[i])
dq.pop_back();
dq.push_back(i);
if(dq.front() - k >= i)
dq.pop_front();
}
ll result(1e18);
for (int i = 0; i <= nArr; ++i)
result = min(result, dpL[i] + dpR[i + 1]);
return result;
}
