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;

class ABC_131_C
{
    static void Main(string[] args)
    {
        string[] input = Console.ReadLine().Split(' ');
        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 c1 = A / C;
        long c2 = B / C;
        long countC = c2 - c1;
        if (A%C==0 && B%C==0) countC++;
        else  if (A%C==0) countC++;

        long d1 = A / D;
        long d2 = B / D;
        long countD = d2 - d1;
        if (A%D==0 && B%D==0) countD++;
        else if (A%D==0) countD++;

        long CD = LCM(C, D);
        long cd1 = A / CD;
        long cd2 = B / CD;
        long countCD = cd2 - cd1;
        if (A%CD==0 && B%CD==0) countCD++;
        else if (A%CD==0) countCD++;

        long ans = B - A + 1 - countC - countD + countCD;

        Console.WriteLine(ans);
    }

    static long GCD(long a, long b)
    {
        if (b == 0) return a;
        return GCD(b, a % b);
    }
    static long LCM(long a, long b)
    {
        return (a * b) / GCD(b, a % b);
    }
}