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: Wrong Answer)

using System;
using System.Text;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
class Program
{
	static void Main(string[] args)
	{
		string[] input = Console.ReadLine().Split(' ');
		ulong A = ulong.Parse(input[0]);
		ulong B = ulong.Parse(input[1]);
		ulong C = ulong.Parse(input[2]);
		ulong D = ulong.Parse(input[3]);
		
		ulong CD = C * D;
		
		ulong[] ans = new ulong[6];
		ulong tr = 1000000000000000000;
		ulong fal = 0;
		while (tr-fal>1)
		{
			ulong mid = (tr + fal) / 2;
			
			if (C*mid>=A) { tr = mid; }
			else { fal = mid; }
            
		}
		ans[0] = tr;
		
		tr = 1000000000000000000;
		fal = 0;
		while (tr-fal>1)
		{
			ulong mid = (tr + fal) / 2;
			
			if (D * mid >= A) { tr = mid; }
			else { fal = mid; }

		}
		ans[1] = tr;
		
		tr = 1000000000000000000;
		fal = 0;
		while (tr-fal>1)
		{
			ulong mid = (tr + fal) / 2;
			
			if (CD * mid >= A) { tr = mid; }
			else { fal = mid; }

		}
		ans[2] = tr;

		
	    tr = 1000000000000000000;
		fal = 0;
		while (tr-fal>1)
		{
			ulong mid = (tr + fal) / 2;
			
			if (C * mid > B) { tr = mid; }
			else { fal = mid; }

		}
		ans[3] = fal;
		
		tr = 1000000000000000000;
		fal = 0;
		while (tr-fal>1)
		{
			ulong mid = (tr + fal) / 2;
			
			if (D * mid > B) { tr = mid; }
			else { fal = mid; }

		}
		ans[4] = fal;
		tr = 1000000000000000000;
		fal = 0;
		while (tr-fal>1)
		{
			ulong mid = (tr + fal) / 2;
			
			if (CD * mid > B) { tr = mid; }
			else { fal = mid; }

		}
		ans[5] = fal;
		if (C > B) { ans[3] = ans[0]; }
		if (D > B) { ans[4] = ans[1]; }
		if (CD > B) { ans[5] = ans[2]; }
		Console.WriteLine(B-A+1-(ans[3] - ans[0] +1+ ans[4] - ans[1]+1 - (ans[5] - ans[2]+1)));
	
	}
	
}