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.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using static System.Console;
using static System.Math;

namespace Atcoder
{
    class Program
    {
        static StreamWriter sw = new StreamWriter(OpenStandardOutput()) { AutoFlush = false };
        static void Main(string[] args)
        {
            try
            {
                SetOut(sw);
                Solve.Answer();
                Out.Flush();
            }
            catch (Exception ex)
            {
                WriteLine(ex.ToString());
            }
        }
    }

    public class Solve
    {
        public static void Answer()
        {
            var abcd = IO.RSLong;
            var a = abcd[0];
            var b = abcd[1];
            var c = abcd[2];
            var d = abcd[3];


            var bc = b / c;
            var bd = b / d;
            var gcd = (long)GCD((int)c, (int)d);
            var bgcd = b / (c * d / gcd);
            var bmade = bc + bd - bgcd;
            var banti = b - bmade;

            var ac = (a - 1) / c;
            var ad = (a - 1) / d;
            var agcd = (a - 1) / (c * d / gcd);
            var amade = ac + ad - agcd;
            var aanti = (a - 1) - amade;

            WriteLine(banti - aanti);

        }

        public class IO
        {
            #region Input
            public static int RInt => int.Parse(ReadLine());
            public static long RLong => long.Parse(ReadLine());
            public static double RDouble => double.Parse(ReadLine());

            public static string[] RSString => ReadLine().Split();
            public static int[] RSInt => ReadLine().Split().Select(s => int.Parse(s)).ToArray();
            public static long[] RSLong => ReadLine().Split().Select(s => long.Parse(s)).ToArray();
            public static double[] RSDouble => ReadLine().Split().Select(s => double.Parse(s)).ToArray();
            #endregion

            #region Output
            public static void OutJoinSpace<T>(IEnumerable<T> list) => WriteLine(string.Join(" ", list));
            public static void WriteLineYes_or_No(bool flag) => WriteLine(flag ? "Yes" : "No");
            public static void WriteLineYES_or_NO(bool flag) => WriteLine(flag ? "YES" : "NO");
            #endregion
        }

        public class Mod
        {
            #region
            private readonly static long M = 1000000007;

            public static long Add(long a, long b) => (a * b) % M;
            public static long Sub(long a, long b) => (a - b) % M >= 0 ? (a - b) % M : (a - b) % M + M;
            public static long Multi(long a, long b) => (a * b) % M;
            #endregion
        }

        public static int GCD(int x, int y)
        {
            if (x < y) Swap(ref x, ref y);
            if (y == 0) return x;
            else return GCD(x % y, y);
        }

        public static void Swap(ref int x, ref int y)
        {
            int tmp = x;
            x = y;
            y = tmp;
        }

        public static long Choice2(long n)
        {
            #region
            if (n <= 1)
                return 0;
            if (n == 2)
                return 1;
            else
                return n * (n - 1) / 2;
            #endregion
        }
    }
}