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().split(' ').map(&:to_i)

def gcd(n, m)
	if n < m
		a = m
		b = n
	else
		a = n
		b = m
	end

	return (a % b == 0 ? b : gcd(b, a % b))
end

lcm = c * d / gcd(c, d)

sum = b - a + 1
sum -= (b * 1.0 / c).floor - (a * 1.0 / c).ceil + 1 if c < b
sum -= (b * 1.0 / d).floor - (a * 1.0 / d).ceil + 1 if d < b
sum += (b * 1.0 / lcm).floor - (a * 1.0 / lcm).ceil + 1 if lcm < b

puts sum