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

class Program
{
    static void Main(string[] args)
    {
        //入力
        long[] d = Console.ReadLine().Split().Select(long.Parse).ToArray();
        long ans = 0;

        //条件を満たすB以下の個数
        //cで割り切れる数
        long tmp1 = d[1] / d[2];
        //dで割り切れる数
        long tmp2 = d[1] / d[3];
        //cdで割り切れる数
        var lcm = Lcm(d[2], d[3]);
        long tmp3 = d[1] / lcm;

        //条件を満たすA-1以下の個数
        //cで割り切れる数
        long tmp4 = (d[0] - 1) / d[2];
        //dで割り切れる数
        long tmp5 = (d[0] - 1) / d[3];
        //cdで割り切れる数
        long tmp6 = (d[0] - 1) / lcm;
        ans = (d[1] - tmp1 - tmp2 + tmp3) - ((d[0] - 1) - tmp4 - tmp5 + tmp6);

        //出力
        Console.WriteLine(ans);
    }

    // 最小公倍数
    public static long Lcm(long a, long b)
    {
        return a * b / Gcd(a, b);
    }

    // ユークリッドの互除法 
    public static long Gcd(long a, long b)
    {
        if (a < b)
            // 引数を入替えて自分を呼び出す
            return Gcd(b, a);
        while (b != 0)
        {
            var remainder = a % b;
            a = b;
            b = remainder;
        }
        return a;
    }
}