Problem:
Score : 300 points

Problem Statement

You are given four integers A, B, C, and D. Find the number of integers between A and B (inclusive) that can be evenly divided by neither C nor D.

Constraints

1\leq A\leq B\leq 10^{18}

1\leq C,D\leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B C D

Output

Print the number of integers between A and B (inclusive) that can be evenly divided by neither C nor D.

Sample Input 1

4 9 2 3

Sample Output 1

2

5 and 7 satisfy the condition.

Sample Input 2

10 40 6 8

Sample Output 2

23

Sample Input 3

314159265358979323 846264338327950288 419716939 937510582

Sample Output 3

532105071133627368

Solution in Ruby (2.3.3) (judge verdict: Accepted)

A, B, C, D = gets.split(' ').map(&:to_i)
lcm = C.lcm(D)
dC = ((B / C) - (A / C))
dC += 1 if A % C == 0
dD = ((B / D) - (A / D))
dD += 1 if A % D == 0
dCD = ((B / lcm) - (A / lcm))
dCD += 1 if A % lcm == 0
p (B - A + 1) - (dC + dD - dCD)