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: Accepted)

using System;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        ulong[] input = Console.ReadLine().Split().Select(i => ulong.Parse(i)).ToArray();
        ulong A = input[0];
        ulong B = input[1];
        ulong C = input[2];
        ulong D = input[3];
        ulong lcm = Lcm(C, D);

        ulong divisible = (B / C + B / D - B / lcm) - ((A - 1) / C + (A - 1) / D - (A - 1) / lcm);

        ulong ans = B - (A - 1) - divisible;

        Console.WriteLine(ans);
    }

    static ulong Lcm(ulong a, ulong b)
    {
        return a * b / Gcd(a, b);
    }

    static ulong Gcd(ulong a, ulong b)
    {
        if (a < b)
        {
            return Gcd(b, a);
        }
        ulong d = 0;
        do {
            d = a % b;
            a = b;
            b = d;
        } while (d != 0);
        return a;
    }
}