package main

import (
	"bufio"
	"os"
	"strconv"
	"strings"
)

func main() {
	stdin := bufio.NewScanner(os.Stdin)
	stdin.Scan()
	slice := strings.Split(stdin.Text(), "")

	if len(slice) < 2 || len(slice) > 9 {
		return
	}

	var bbb [][]string
	bbb = append(bbb, []string{})
	for k, str := range slice {
		a, _ := strconv.Atoi(str)
		if a <= 0 {
			return
		}

		ccc := make([][]string, len(bbb[0]))
		var ddd []string
		var eee []string

		if k == 0 {
			ddd = append(ddd, str)
		}
		for i, b := range bbb[0] {
			ddd = append(ddd, str)
			for j, _ := range ccc {
				if i == j {
					ccc[j] = append(ccc[j], str)
					eee = append(eee, b)
				} else {
					ccc[j] = append(ccc[j], b)
				}
			}
		}
		ddd = append(ddd, eee...)
		bbb = append(bbb, ccc...)
		for i, a := range ddd {
			bbb[i] = append(bbb[i], a)
		}
	}

	max := 0
	for _, k := range bbb {
		buf := ""
		for _, kk := range k {
			buf += kk
		}
		a, _ := strconv.Atoi(buf)
		if max < a {
			max = a
		}
	}
	println(max)
}