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;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var ss = Console.ReadLine().Split();
            var A = long.Parse(ss[0]);
            var B = long.Parse(ss[1]);
            var C = long.Parse(ss[2]);
            var D = long.Parse(ss[3]);
            var c = C;
            var d = D;

            var x = c * d;

            if (c < d)
            {
                var tmp = c;
                c = d;
                d = tmp;
            }

            var r = c % d;
            while (r != 0)
            {
                c = d;
                d = r;
                r = c % d;
            }

            var CD = x / d;

            var countB = (B / C) + (B / D) - (B / CD);
            var countA = ((A - 1) / C) + ((A - 1) / D) - ((A - 1) / CD);

            Console.WriteLine((B - A + 1) - (countB - countA));
        }
    }
}