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)

// C - Anti-Division
//20190913

using System;
using System.Linq;
using static System.Math;

namespace C
{
    class Program
    {
        static void Main(string[] args)
        {
            long[] abcd = Console.ReadLine().Split().Select(long.Parse).ToArray();
            long a = abcd[0];
            long b = abcd[1];
            int c = (int)abcd[2];
            int d = (int)abcd[3];

            long numOfMultipleC = NumOfMultiple(a, b, c);
            long numOfMultipleD = NumOfMultiple(a, b, d);

            long leastCommonMultipleCD = LeastCommonMultiple(c, d);
            long numOfMultipleCD = NumOfMultiple(a, b, leastCommonMultipleCD);

            long ans = b - a + 1 - numOfMultipleC - numOfMultipleD + numOfMultipleCD;

            Console.WriteLine(ans);

        }

        static long NumOfMultiple(long min, long max, long div)
        {
            return (max / div) - ((min - 1) / div);

            // long minMultiple = 0;

            // for (long i = a; i < a + c && i < b; i++)
            // {
            //     if (i % c == 0)
            //     {
            //         minMultiple = i;
            //         return (long)(int)(1 + ((b - minMultiple) / c));
            //     }
            // }
            // return 0;
        }

        static long LeastCommonMultiple(long m, long n)
        {

            return m / GCD(m, n) * n;
        }

        static long GCD(long m, long n)
        {
            while (true)
            {
                if(n == 0) return m;
                m %= n;
                if(m == 0) return n;
                n %= m;
            }
        }
    }
}