Contest: Task: Related: TaskB

Score : $100$ points

There is a hotel with the following accommodation fee:

- $X$ yen (the currency of Japan) per night, for the first $K$ nights
- $Y$ yen per night, for the $(K+1)$-th and subsequent nights

Tak is staying at this hotel for $N$ consecutive nights. Find his total accommodation fee.

- $1 \leq N, K \leq 10000$
- $1 \leq Y < X \leq 10000$
- $N,\,K,\,X,\,Y$ are integers.

The input is given from Standard Input in the following format:

$N$ $K$ $X$ $Y$

Print Tak's total accommodation fee.

5 3 10000 9000

48000

The accommodation fee is as follows:

- $10000$ yen for the $1$-st night
- $10000$ yen for the $2$-nd night
- $10000$ yen for the $3$-rd night
- $9000$ yen for the $4$-th night
- $9000$ yen for the $5$-th night

Thus, the total is $48000$ yen.

2 3 10000 9000

20000