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.Text;
using System.Numerics;

namespace cc
{
    class Program
    {
        // LCM
        public static long Lcm(long a, long b)
        {
            return a * b / Gcd(a, b);
        }

        // GCD
        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;
        }

        static void Main(string[] args)
        {
            string[] strs = Console.ReadLine().Split(' ');

            long A = long.Parse(strs[0]);
            long B = long.Parse(strs[1]);
            long C = long.Parse(strs[2]);
            long D = long.Parse(strs[3]);

            long E = Lcm(C, D);

            long ans = B / C - (A - 1) / C +
                       B / D - (A - 1) / D -
                       (B / E - (A - 1) / E);

            ans = B - A + 1 - ans;

            Console.WriteLine(ans);
        }
    }
}