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: Accepted)

def gcd(a, b)
    r = a % b
    while r != 0 do
        a = b
        b = r
        r = a % b
    end
    return b
end

a, b, c, d = gets.chomp.split(" ").map(&:to_i)
e = c * d / gcd(c, d)

can_c = b/c - (a-1)/c
can_d = b/d - (a-1)/d
can_e = b/e - (a-1)/e

cannot = (b - a + 1) - (can_c + can_d - can_e)
puts cannot