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 questionC
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            var line1 = Console.ReadLine().Split(' ');
            var A = Int64.Parse(line1[0]);
            var B = Int64.Parse(line1[1]);
            var C = Int32.Parse(line1[2]);
            var D = Int32.Parse(line1[3]);

            var all = B - A + 1;
            var CCount = Count(A, B, C);
            var DCount = Count(A, B, D);
            var LCM = Lcm(C, D);
            var CDCount = Count(A, B, LCM);
            var canDevide = CCount + DCount - CDCount;

            Console.WriteLine(all - canDevide);

        }

        public static long Lcm(long a, long b)
        {
            long GCD = Gcd(a, b);
            long ab = a * b;
            long val = ab / GCD;
            return val;
        }

        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 long Count(long A, long B, long n)
        {
            if (n < 0)
            {
                return 0;
            }
            var Adev = A / n;
            var Bdev = B / n;
            if (A % n == 0)
            {
                return Bdev - Adev + 1;
            }
            else
            {
                return Bdev - Adev;
            }
        }
    }
}