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;

namespace C___Anti_Division
{
    class Program
    {
        static void Main(string[] args)
        {
            var A_B_C_D = Console.ReadLine().Split().Select(decimal.Parse).ToArray();
            decimal A = A_B_C_D[0], B = A_B_C_D[1], C = A_B_C_D[2], D = A_B_C_D[3];
            decimal E = Lcm(C, D);
            decimal res = 0;

            decimal cnt_C = Math.Floor(B / C) - Math.Ceiling(A / C) + 1;
            decimal cnt_D = Math.Floor(B / D) - Math.Ceiling(A / D) + 1;
            decimal cnt_E = Math.Floor(B / E) - Math.Ceiling(A / E) + 1;

            res = B - A + 1 - (cnt_C + cnt_D - cnt_E);
            Console.WriteLine(res);
        }

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

        static decimal Gcd(decimal a, decimal b)
        {
            if (a == 0) return b;
            if (b == 0) return a;

            return a > b ? GcdRecursive(a, b) : GcdRecursive(b, a);
        }

        static decimal GcdRecursive(decimal l, decimal r) => r == 0 ? l : GcdRecursive(r, l % r);
    }
}