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 (2.7.1) (judge verdict: Accepted)

def gcd(a,b)
  if b == 0
    a
  else
    gcd(b,a%b)
  end
end
def lcm(a,b)
  a*b/gcd(a,b)
end
a,b,c,d = gets.chomp.split(" ").map(&:to_i)
sum = b-a+1
sum_c = b/c - (a-1)/c
sum_d = b/d - (a-1)/d
e = lcm(c,d)
sum_e = b/e - (a-1)/e
puts sum - sum_c - sum_d + sum_e