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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections;

namespace ConsoleApp1
{
    class Program
    {
        //最大公約数
        static long lcm(long a, long b)
        {
            return a * b / god(a, b);
        }
        //最小公倍数
        static long god (long a, long b)
        {
            if (a < b)
            {
                long tmp = a;
                a = b;
                b = tmp;
            }

            // ユークリッドの互除法
            long r = a % b;
            while (r != 0)
            {
                a = b;
                b = r;
                r = a % b;
            }
            return b;

        }

        // a～bまでにcの倍数がいくつあるかを返す
        static long calc(long a, long b, long c)
        {
            long n = b - a + 1;
            long ans = n / c;

            long ama1 = a % c;
            long ama2 = n % c;
            if (ama1 < ama2) ans++;

            return ans;
        }
        static void Main(string[] args)
        {
          
            long[] inp = Array.ConvertAll(Console.ReadLine().Split(), long.Parse);

            long a = inp[0];
            long b = inp[1];
            long c = inp[2];
            long d = inp[3];
            long n1 = calc(a, b, c);
            long n2 = calc(a, b, d);
            long n3 = calc(a, b, lcm(c, d));

            long ans = (b - a + 1) + n3 - n1 - n2;

            Console.WriteLine(ans);
        }
    }
}