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.strip.split(" ").map(&:to_i)

coff = (a / c.to_f).ceil * c
cc = 
  if b - coff >= 0
    (b - coff) / c + 1
  else
    0
  end

doff = (a / d.to_f).ceil * d
dc = 
  if b - doff >= 0
    (b - doff) / d + 1
  else
    0
  end

x = c * d / c.gcd(d)
xoff = (a / x.to_f).ceil * x
xc = 
  if b - xoff >= 0
    (b - xoff) / x + 1
  else
    0
  end

puts ((b - a) + 1 - (cc + dc - xc)).to_i