package main

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

var sc = bufio.NewScanner(os.Stdin)
var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func main() {
	sc.Split(bufio.ScanWords)
	n, _ := nextInt(), nextInt()
	max := 0
	for i := 1; i <= n/2; i++ {
		g := gcd(i, n-i)
		if g > max {
			max = g
		}
	}
	fmt.Println(max)
}

func nextLine() string {
	sc.Scan()
	return sc.Text()
}

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

func gcd(a, b int) int {
	for ; b != 0; b, a = a%b, b {
	}
	return a
}