Problem Statement

There are two 100-story buildings, called A and B. (In this problem, the ground floor is called the first floor.)
For each $i = 1,\dots, 100$, the i-th floor of A and that of B are connected by a corridor.
Also, for each $i = 1,\dots, 99,$ there is a corridor that connects the (i+1)-th floor of A and the i-th floor of B.
You can traverse each of those corridors in both directions, and it takes you x minutes to get to the other end.
Additionally, both of the buildings have staircases. For each $i = 1,\dots, 99, a$ staircase connects the i-th and (i+1)-th floors of a building, and you need y minutes to get to an adjacent floor by taking the stairs.
Find the minimum time needed to reach the b-th floor of B from the a-th floor of A.

Input

Input is given from Standard Input in the following format:
a b x y

Output

Print the minimum time needed to reach the b-th floor of B from the a-th floor of A.

Constraints

• $1 \leq a,b,x,y \leq 100$
• All values in input are integers.

Sample Input 1

2 1 1 5

Sample Output 1

1

There is a corridor that directly connects the 2-nd floor of A and the 1-st floor of B, so you can travel between them in 1 minute.
This is the fastest way to get there, since taking the stairs just once costs you 5 minutes.

Sample Input 2

1 2 100 1

Sample Output 2

101

For example, if you take the stairs to get to the 2-nd floor of A and then use the corridor to reach the 2-nd floor of B, you can get there in 1+100=101 minutes.

Sample Input 3

1 100 1 100

Sample Output 3

199

Using just corridors to travel is the fastest way to get there.

见题面 Input 部分

见题面 Output 部分