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;
class Program
    {
        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 void Main(string[] args)
        {
            string[] s1 = Console.ReadLine().Split(' ');
            long a = long.Parse(s1[0]), b = long.Parse(s1[1]), c = long.Parse(s1[2]), d = long.Parse(s1[3]);

            long ans = b / c - (a - 1) / c;
            ans += b / d - (a - 1) / d;
            long cd = c * d / Gcd(c, d);

            ans -= b / cd - (a - 1) / cd;
            Console.WriteLine(b - a + 1 - ans);
            
        }
    }
    //mcs Main.cs
    //mono Main.exe