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.Numerics;

namespace atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var abcd = Console.ReadLine().Split(' ').Select(num => long.Parse(num)).ToArray();

            var a = abcd[0];
            var b = abcd[1];
            var c = abcd[2];
            var d = abcd[3];

            var cCnt = Calc(a, b, c);
            var dCnt = Calc(a, b, d);
            var cdCnt = Calc(a, b, c * d / Gcd(c, d));

            Console.WriteLine(b - a + 1 - (cCnt + dCnt - cdCnt));
        }

        private static long Gcd(long a, long b)
        {
            var big = Math.Max(a, b);
            var small = Math.Min(a, b);

            var tmp = big % small;
            if (tmp == 0)
            {
                return small;
            }
            else
            {
                return Gcd(small, tmp);
            }
        }
        private static long Calc(long a, long b, long n)
        {
            var result = (b / n) - (a / n);
            if (a % n == 0) result++;

            return result;
        }
    }
}