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 abc131_c
{
    class Program
    {
        static void Main(string[] args)
        {
            var ABCD = Console.ReadLine().Split(' ').Select(x => decimal.Parse(x)).ToList();

            decimal A = ABCD[0];
            decimal B = ABCD[1];
            decimal C = ABCD[2];
            decimal D = ABCD[3];

            var CL = new List<long>();
            var DL = new List<long>();
            var EL = new List<long>();

            var CC = Math.Floor(B / C) - Math.Floor(A / C); //Cの倍数の数
            if (A % C == 0) CC++;
            
            decimal DC = 0;
            decimal LCMC = 0;

            if ( C != D) 
            {
                DC = Math.Floor(B / D) - Math.Floor(A / D); //Dの倍数の数
                if (A % D == 0) DC++;

                var LCM = Lcm(C, D); // C,Dの最小公倍数
                LCMC = Math.Floor(B / LCM) - Math.Floor(A / LCM); //最小公倍数の倍数の数
                if (A % LCM == 0) LCMC++;
            }

            Console.WriteLine(B - A + 1 - (CC + DC - LCMC));
        }

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

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

    }
}