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: Runtime Error)

def gcd(a, b)
  r = a % b
  while r > 0
    a = b
    b = r
    r = a % b
  end
  return r
end
A, B, C, D = gets.split.map!(&:to_i)
num = B - A + 1
GCD = if C - D > 0
    gcd(C, D)
  else
    gcd(D, C)
  end
2.times do |i|
  num -= (B - A + 1) / nums[i]
end
num += (B - A + 1) / GCD
puts num