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;
using System.Collections.Generic;
namespace Collections
{
	class program
	{
		static void Main(string[] args)
		{
			// 入力
			string[] input = Console.ReadLine().Split(' '); // N, a
			long A = long.Parse(input[0]);
			long B = long.Parse(input[1]);
			long C = long.Parse(input[2]);
			long D = long.Parse(input[3]);

			long multC = B/C - (A-1)/C; //A->Bに含まれるCの倍数は
			long multD = B/D - (A-1)/D; //A->Bに含まれるDの倍数

			// C,Dの最小公倍数を求める
			long gcd = getGCD(C,D);
			long lcm = C*D/gcd;
			long multCD = B/lcm - (A-1)/lcm;

			long num = (B-A+1) - multC - multD + multCD;
			Console.WriteLine(num + "");
    }
		static long getGCD(long a, long b)
		{
			if(a%b == 0)
				return b;

			return getGCD(b, a%b);
		}
	}
}