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.Linq;
using System.Collections.Generic;

namespace AtCoder
{
    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]);
            
            Console.WriteLine((get_count(B, C, D) - get_count(A-1, C, D)).ToString());
        }
        public static long get_count(long X, long C, long D)
        {
            return X - X / C - X / D + X / Lcm(C, D);
        }
        // Gratest Common Divider by Euclid 
        public static long Gcd(long a, long b)
        {
            if (a < b)
                return Gcd(b, a);
            while (b != 0)
            {
                var remainder = a % b;
                a = b;
                b = remainder;
            }
            return a;
        }
        // Least Common Multiplier
        public static long Lcm(long a, long b)
        {
            return a * b / Gcd(a, b);
        }
    }
}