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)

def gcd(a, b)
  r = a % b
  r.zero? ? b : gcd(b, r)
end

a, b, d, e = gets.split.map(&:to_i)
g = d * e / gcd(d, e)
m = b - a + 1
cnt1 = (m * 1.0 / d - 0.1 ** 10).round
cnt2 = (m * 1.0 / e - 0.1 ** 10).round
cnt3 = (m * 1.0 / g - 0.1 ** 10).round
puts m - (cnt1 + cnt2 - cnt3)