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: Wrong Answer)

A, B, C, D = gets.chomp.split.map(&:to_i)

lcm = C.lcm(D)
lcm = [C, D].min if D == lcm || C == lcm
undivided = lcm - (lcm / C + lcm / D - 1)

# 0...A
q, r = (A - 1).divmod(lcm)
a = q * undivided + (r - (r / C  + r / D))

# 0..B
q, r = B.divmod(lcm)
b = q * undivided + (r - (r / C  + r / D))

puts b - a