Problem Statement

Takahashi had his N-th birthday, when he was T centimeters tall.
Additionally, we know the following facts:

• In each year between Takahashi's birth (0-th birthday) and his X-th birthday, his height increased by D centimeters. More formally, for each $i = 1, 2, \ldots, X,$ his height increased by D centimeters between his (i-1)-th birthday and his i-th birthday.
• Between Takahashi's X-th birthday and his N-th birthday, his height did not change.

Find Takahashi's height on his M-th birthday, in centimeters.

Input

Input is given from Standard Input in the following format:
N M X T D

Output

Print the answer as an integer.

Constraints

• $0 \leq M \lt N \leq 100$
• $1 \leq X \leq N$
• $1 \leq T \leq 200$
• $1 \leq D \leq 100$
• Takahashi was at least 1 centimeter tall at his birth.
• All values in input are integers.

Sample Input 1

38 20 17 168 3

Sample Output 1

168

In this sample, Takahashi was 168 centimeters tall on his 38-th birthday. Also, his height did not change between his 17-th birthday and 38-th birthday.
From these facts, we find that he was 168 centimeters tall on his 20-th birthday, so the answer is 168.

Sample Input 2

1 0 1 3 2

Sample Output 2

1

In this sample, Takahashi was 1 centimeter tall on his 0(=M)-th birthday and 3(=T) centimeters tall on his 1(=N)-st birthday.

Sample Input 3

100 10 100 180 1

Sample Output 3

90

见题面 Input 部分

见题面 Output 部分