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;
class Program
{
	static void Main(string[] args)
	{
		string[] str = Console.ReadLine().Split();
		long A = long.Parse(str[0])-1;
		long B = long.Parse(str[1]);
		long C = long.Parse(str[2]);
		long D = long.Parse(str[3]);
		long L = Lcm(C,D);
		long a1 = B - B/C - B/D + B/L;
		long a2 = A - A/C - A/D + A/L;
		Console.WriteLine(a1-a2);
	}
	
	public static long Gcd(long a, long b) {
		if (a < b)
			return Gcd(b, a);
		while (b != 0) {
			var r = a % b;
			a = b;
			b = r;
		}
		return a;
	}
	public static long Lcm(long a, long b) {
        return a * b / Gcd(a, b);
    }
}