package main

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

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

func main() {
	sc.Split(bufio.ScanWords)
	k, n := nextInt(), nextInt()
	ps := eratosthenes(n)
	for i, v := range ps {
		if v >= k {
			ps = ps[i:]
			break
		}
	}

	h := make([]int, len(ps))
	for i, v := range ps {
		h[i] = hash(v)
	}

	m := make([]int, 10)
	l, tmp := 0, 0
	c := make([]int, 2)

	for i, v := range h {
		if m[v] != 0 {
			if tmp >= c[0] {
				c = []int{tmp, l}
			}
			tmp -= m[v] - l
			tmp++
			tmpL := l
			l = m[v]
			for _, v := range h[tmpL:m[v]] {
				m[v] = 0
			}

			m[v] = i + 1
			continue
		}
		m[v] = i + 1
		tmp++
	}

	if tmp >= c[0] {
		c = []int{tmp, l}
	}

	fmt.Println(ps[c[1]])
}

func hash(i int) int {
	n := 0
	for ; i > 0; i /= 10 {
		n += i % 10
	}
	if n >= 10 {
		return hash(n)
	}
	return n
}

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

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

func eratosthenes(n int) []int {
	if n < 2 {
		return []int{}
	}

	r := int(math.Floor(math.Sqrt(float64(n))))
	list := make([]bool, n+1)
	list[0], list[1] = true, true

	for i := 2; i <= r; i++ {
		if !list[i] {
			for j := i * i; j <= n; j += i {
				list[j] = true
			}
		}
	}

	l := n / int(math.Ceil(math.Log(float64(n))))
	primes := make([]int, 0, l)
	for i, v := range list {
		if v {
			continue
		}
		primes = append(primes, i)
	}

	return primes
}