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

namespace ConsoleApp135 {
    class Program {
        static void Main(string[] args) {
            //入力
            string s = Console.ReadLine();

            long A = long.Parse(s.Split(' ')[0]);
            long B = long.Parse(s.Split(' ')[1]);
            long C = long.Parse(s.Split(' ')[2]);
            long D = long.Parse(s.Split(' ')[3]);

            //解答となる数値
            long ans = 0;

            //CとDが互いに倍数関係になっているかで場合分けする
            if (LCM(C, D) == C || LCM(C, D) == D) {
                ans = B / Math.Min(C, D) - (A - 1) / Math.Min(C, D);
            } else {
                ans = (B / C + B / D - B / LCM(C, D)) - ((A - 1) / C + (A - 1) / D - (A - 1) / LCM(C, D));
            }


            Console.WriteLine(B - A + 1 - ans);
        }
        //最小公倍数
        public static long LCM(long a, long b) {
            return a * b / GCD(a, b);
        }

        //最大公約数
        public static long GCD(long a, long b) {
            if (a < b) {
                return GCD(b, a);
            }

            while(b != 0) {
                long remainder = a % b;
                a = b;
                b = remainder;
            }
            return a;
        }
    }
}