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.Text;

namespace AtCoder
{
	public class Program
	{
		// ABC131-C
		static void Main(string[] args)
		{
			string str = Console.ReadLine();
			string[] vs = str.Split();

			long a = long.Parse(vs[0]), b = long.Parse(vs[1]), c = long.Parse(vs[2]), d = long.Parse(vs[3]);

			long countC = b / c - (a - 1) / c;
			long countD = b / d - (a - 1) / d;
			long lcm = LCM(c, d);
			long countCD = b / lcm - (a - 1) / lcm;

			long count = (b - a + 1) - countC - countD + countCD;

			Console.WriteLine(count);
		}

		public static long LCM(long m, long n)
		{
			if (m < n) {
				long tmp = m;
				m = n;
				n = tmp;
			}
			return m * n / GCD(m, n);
		}

		public static long GCD(long m, long n)
		{
			if (m < n) {
				long tmp = m;
				m = n;
				n = tmp;
			}
			if (n == 0) {
				return m;
			}
			return GCD(n, m % n);
		}
	}
}