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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var scanner = bufio.NewScanner(os.Stdin)

func next() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	i, _ := strconv.Atoi(next())
	return i
}

func gcd(a int64, b int64) int64 {
	if b == 0 {
		return a
	}
	return gcd(b, a%b)
}

func lcm(a int64, b int64) int64 {
	return a / gcd(a, b) * b
}

func calc(sum int64, c int64, d int64) int64 {
	divC := sum / c
	divD := sum / d
	divCD := sum / lcm(c, d)
	return (sum - divC - divD + divCD)
}

func main() {
	scanner.Split(bufio.ScanWords)

	a := int64(nextInt())
	b := int64(nextInt())
	c := int64(nextInt())
	d := int64(nextInt())

	if a == 1 {
		sum := b
		fmt.Println(calc(sum, c, d))
	} else {
		sum1 := a - 1
		cal1 := calc(sum1, c, d)

		sum2 := b
		cal2 := calc(sum2, c, d)
		fmt.Println(cal2 - cal1)
	}
}