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 ProblemC
{
    class Program
    {
        static void Main(string[] args)
        {
            var read = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
            var A = read[0];
            var B = read[1];
            var C = read[2];
            var D = read[3];

            var allNumsCount = B - A + 1;
            var lcm = Lcm(C, D);
            var CCount = A % C == 0 ? B / C - A / C + 1 : B / C - A / C;
            var DCount = A % D == 0 ? B / D - A / D + 1 : B / D - A / D;
            var lcmCount = A % lcm == 0 ? B / lcm - A / lcm + 1 : B / lcm - A / lcm;
            Console.WriteLine(allNumsCount - (CCount + DCount - lcmCount));
        }

        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;
        }
    }
}