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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Linq;
using System.Collections.Generic;

using E = System.Linq.Enumerable;

public class Program
{
    public static void Main()
    {
        var abcd = Console.ReadLine().Split().Select(x => long.Parse(x)).ToArray();
        var a = abcd[0];
        var b = abcd[1];
        var c = abcd[2];
        var d = abcd[3];

        var ab = b - a;
        var n = ab / c + (ab % c == 0 && a % c == 0 ? 1 : 0);
        var m = ab / d + (ab % d == 0 && a % d == 0 ? 1 : 0);
        var cd = c * d;

        var cc = c;
        var dd = d;
        while (dd > 0)
        {
            if (cc > dd)
            {
                cc += dd;
                dd = cc - dd;
                cc -= dd;
            }
            dd %= cc;
        }
        var gcd = cc;
        var lcm = c / gcd * d;
        var l = ab / lcm + (ab % lcm == 0 && a % lcm == 0 ? 1 : 0);
        Console.WriteLine(ab - n - m + l);
    }
}