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.Collections.Generic;
using System.Linq;
using static System.Console;
using static System.Math;

class Program
{
    static void Main()
    {
        var ABCD = ReadLine().Split().Select(long.Parse).ToArray();
        var A = ABCD[0];
        var B = ABCD[1];
        var C = ABCD[2];
        var D = ABCD[3];
        A--;
        var gcd = GCD(C, D);
        var lcm = C / gcd * D;
        var a = A - A / C - A / D + A / lcm;
        var b = B - B / C - B / D + B / lcm;
        WriteLine(b - a);
    }

    static long GCD(long a, long b) => b == 0 ? a : GCD(b, a % b);
}