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;

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

            var l = Lcm(C, D);
            var underB = B - B / C - B / D + B / l;
            var lessA = A - A / C - A / D + A / l;

            Console.WriteLine(underB - lessA);
        }

        static long Gcd(long m, long n)
        {
            long tmp;
            while (m % n != 0)
            {
                tmp = n;
                n = m % n;
                m = tmp;
            }
            return n;
        }

        static long Lcm(long m, long n)
        {
            return m * n / Gcd(m, n);
        }
    }
}