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)

# aからbの中のcの倍数
cc = (b-a)/c + 1
# aからbの中のdの倍数
cd = (b-a)/d + 1
lcm = c*d / c.gcd(d)
# aからbの中のlcm(c,d)の倍数
ccd = (b-a)/lcm + 1

ans = b-a+1
" 
cでもdでも割り切れない数
= 全体の数-cで割り切れる数-dで割り切れる数+cでもdでも割り切れる数
"
ans -= (cc+cd-ccd)
puts ans