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 ABC131C
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split();
            long A = long.Parse(input[0]);
            long B = long.Parse(input[1]);
            long C = long.Parse(input[2]);
            long D = long.Parse(input[3]);

            long lcm = LCM(C, D);

            long AC = (A-1) / C;
            long AD = (A-1) / D;
            long A_lcm = (A-1) / lcm;
            long BC = B / C;
            long BD = B / D;
            long B_lcm = B / lcm;

            long ans =  B-(BC + BD - B_lcm)-(A-1-(AC + AD - A_lcm));
            Console.WriteLine(ans);
        }
        // Least Common Multiple　最小公倍数
        static long LCM(long a, long b)
        {
            return a * b / GCD(a, b);
        }
        // Greatest Common Divisor 最大公約数
        // ユークリッドの互除法
        static long GCD(long a, long b)
        {
            if (b == 0)
            {
                return a;
            }
            else
            {
                return GCD(b, a % b);
            }
        }
    }
}