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;

namespace atCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var input = Console.ReadLine().Split(' ');
            long min = long.Parse(input[0]);
            long max = long.Parse(input[1]);
            long div1 = int.Parse(input[2]);
            long div2 = int.Parse(input[3]);

            long count = max - min + 1;
            long num_div1 = GetMultiples(min, max, div1);
            long num_div2 = GetMultiples(min, max, div2);
            long num_dup = GetMultiples(min, max, GetLeastCommonMultiple(div1,div2));

            long result = count - num_div1 - num_div2 + num_dup;
            Console.WriteLine(result);
        }

        //min-max間のdivの倍数の数
        static long GetMultiples(long min,long max, long div)
        {
            long minmultiple = min + (min % div == 0 ? 0 : (div - min % div));
            long maxmultiple = max - max % div;
            return (maxmultiple - minmultiple) / div + 1;
        }

        //最小公倍数
        static long GetLeastCommonMultiple(long a, long b)
        {
            long x = a * 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 x/b;
        }
    }
}