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 System.Text;
using System.Threading.Tasks;

namespace ABC131A
{
    class Program
    {
        static void Main(string[] args)
        {
            var abcd = Console.ReadLine().Split(' ');
            var a = ulong.Parse(abcd[0]);
            var b = ulong.Parse(abcd[1]);
            var c = ulong.Parse(abcd[2]);
            var d = ulong.Parse(abcd[3]);
            var cdlcm = Lcm(c, d);
            var tmp = b / c - (a - 1) / c + b / d - (a - 1) / d - (b / cdlcm - (a - 1) / cdlcm);
            var result = b - a + 1 - tmp;
            Console.WriteLine(result);

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

        // ユークリッドの互除法 
        public static  ulong Gcd( ulong a,  ulong 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;
        }
    }
}