11213: ABC374 - F - Shipping
Description
KEYENCE is famous for quick delivery.
In this problem, the calendar proceeds as Day $1$, Day $2$, Day $3$, $\dots$.
There are orders $1,2,\dots,N$, and it is known that order $i$ will be placed on Day $T_i$.
For these orders, shipping is carried out according to the following rules.
- At most $K$ orders can be shipped together.
- Order $i$ can only be shipped on Day $T_i$ or later.
- Once a shipment is made, the next shipment cannot be made until $X$ days later.
- That is, if a shipment is made on Day $a$, the next shipment can be made on Day $a+X$.
For each day that passes from order placement to shipping, dissatisfaction accumulates by $1$ per day.
That is, if order $i$ is shipped on Day $S_i$, the dissatisfaction accumulated for that order is $(S_i - T_i)$.
Find the minimum possible total dissatisfaction accumulated over all orders when you optimally schedule the shipping dates.
Input
The input is given from Standard Input in the following format:
$N$ $K$ $X$
$T_1$ $T_2$ $\dots$ $T_N$
Output
Constraints
- All input values are integers.
- $1 \le K \le N \le 100$
- $1 \le X \le 10^9$
- $1 \le T_1 \le T_2 \le \dots \le T_N \le 10^{12}$
Sample 1 Input
5 2 3
1 5 6 10 12
Sample 1 Output
2
For example, by scheduling shipments as follows, we can achieve a total dissatisfaction of $2$, which is the minimum possible.
- Ship order $1$ on Day $1$.
- This results in dissatisfaction of $(1-1) = 0$, and the next shipment can be made on Day $4$.
- Ship orders $2$ and $3$ on Day $6$.
- This results in dissatisfaction of $(6-5) + (6-6) = 1$, and the next shipment can be made on Day $9$.
- Ship order $4$ on Day $10$.
- This results in dissatisfaction of $(10-10) = 0$, and the next shipment can be made on Day $13$.
- Ship order $5$ on Day $13$.
- This results in dissatisfaction of $(13-12) = 1$, and the next shipment can be made on Day $16$.
Sample 2 Input
1 1 1000000000
1000000000000
Sample 2 Output
0
Sample 3 Input
15 4 5
1 3 3 6 6 6 10 10 10 10 15 15 15 15 15
Sample 3 Output
35