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.Threading.Tasks;


class maki {
	//最大公約数
	static long gcd(long x,long y){
    	if(y==0){
    		return x;
    	}
    	return gcd(y,x%y);
    }

    static void Main(string[] args) {
        var cin=Console.ReadLine().Split().Select(long.Parse).ToArray();
        //int n = int.Parse(Console.ReadLine());
        //string s=Console.ReadLine();
 
        long a=cin[0];
        long b=cin[1];
        long c=cin[2];
        long d=cin[3];
        long e=c*d/gcd(c,d);//最小公倍数
        a--;
        long ans= b-((b/c)+(b/d)-(b/e));//b以下について
        ans-= a-((a/c)+(a/d)-(a/e));//a未満(a-1以下)の数を引く
        Console.WriteLine(ans);
    }
}