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.IO;
using System.Text;
using static System.Console;
using static System.Math;

namespace AtCodeeeer
{
    class AtCOOOOOOOOOOOder
    {
        static void Main(string[] args)
        {
            long[] s = ReadLine().Split(' ').Select(long.Parse).ToArray();

            long n1 = calc(s[0], s[1], s[2]);
            long n2 = calc(s[0], s[1], s[3]);
            long n3 = calc(s[0], s[1], Lcm(s[2],s[3]));



            WriteLine(
                (s[1] - s[0] + 1) + n3 - n1 - n2
                ) ;
        }

        static long calc(long a, long b, long c)
        {
            long n = b - a + 1;
            long ans = b / c - (a - 1) / c;

            return ans;
        }


        static long Gcd(long a, long b)
        {
            var v = new[] { a, b };
            while (v[1] != 0) { v = new[] { v[1], v[0] % v[1] }; }
            return v[0];
        }

        /*
         * Lcm (Last Common Multiple) 最小公倍数 
         * Gcdライブラリの仕様が前提
        */

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