#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
const int MAX = 10000007;
ll P[MAX], L[MAX], R[MAX];
ll delivery(int N, int K, int M, int* _P) {
for (int i = 1; i <= N; ++i) L[i] = P[i] = _P[i - 1];
for (int i = 1; i <= N; ++i) if (K <= i) L[i] += L[i - K];
P[N + 1] = M;
for (int i = N + 1; i > 0; --i) {
R[i] = M - P[i];
if (i + K <= N + 1) R[i] += R[i + K];
}
ll ret = 1e18;
for (int i = 0; i <= N; ++i) ret = min(ret, 2 * (L[i] + R[i + 1]));
for (int i = 1; i + K <= N + 1; ++i) {
ret = min(ret, M + (L[i - 1] + R[i + K]) * 2);
}
return ret;
}
