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 PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
  function gcd($m, $n){
    if($n > $m) list($m, $n) = array($n, $m);
     
    while($n !== 0){
        $tmp_n = $n;
        $n = $m % $n;
        $m = $tmp_n;
    }
    return $m;
}
 
//最小公倍数
function lcm($m, $n){
    return $m * $n / gcd($m, $n);
}
  
 fscanf(STDIN,"%d%d%d%d",$a,$b,$c,$d);
 $b2 = floor($b/$c)+floor($b/$d)-floor($b/lcm($c,$d));
 $a2 = floor(($a-1)/$c)+floor(($a-1)/$d)-floor(($a-1)/lcm($c,$d));

$b = $b-$b2;
$a = $a-1-$a2;
echo $b-$a;