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.Diagnostics;
using System.IO;
using System.Text;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args) {
#if DEBUG
        //MyDebugger.MakeTestCase("../TextFile2.txt"); return;
        MyDebugger.Test(process, "../TextFile1.txt");
#else
        object ret = process(new StreamReader(Console.OpenStandardInput()));
        Console.WriteLine(ret);
#endif
    }

    static object process(TextReader input) {
        var spl = input.ReadLine().Split(' ');
        var a = long.Parse(spl[0]);
        var b = long.Parse(spl[1]);
        var c = long.Parse(spl[2]);
        var d = long.Parse(spl[3]);

        long l = b - a;

        long perC = Count(a, b, c);
        //Debug.Write(perC);
        //Debug.Write(" ");

        long perD = Count(a, b, d);
        //Debug.Write(perD);
        //Debug.Write(" ");

        long perCD = Count(a, b, LCM(c, d));
        //Debug.Write(perCD);
        //Debug.Write(" ");
        //Debug.WriteLine(" ");

        return l-(perC+perD-perCD);
    }

    static long Count(long a, long b, long n) {
        if(n > b) return 0;

        long f = a;
        if(a % n != 0) f = a + (n - a % n);

        if (f > b) return 0;
        return (b - f) / n;
    }

    static long LCM(long a, long b) {
        var x = a * b;
       
      if(a<b){
        var tmp = a;
        a = b;
        b = tmp;
      }
 
      /* ユークリッドの互除法 */
      var r = a % b;
      while(r!=0){
        a = b;
        b = r;
        r = a % b;
      }
 
      return x/b;
    }

}