package main

import (
	"fmt"
	"sort"
	"strings"
)

func main() {
	var S string
	fmt.Scan(&S)
	A := "abcdefghijklm"
	s := strings.Split(S, "")
	a := strings.Split(A, "")
	sort.Strings(s)
	S = strings.Join(s, "")
	sort.Strings(a)
	count := make([]int, 13)
	var e, d bool
	for i := 0; i < 13; i++ {
		n := int(S[i] - 'a')
		if n > 12 {
			e = true
			break
		}
		count[n]++
		if count[n] > 2 {
			e = true
			break
		}
		if count[n] == 2 {
			d = true
		}
	}
	// log.Println(s)
	// log.Println(a)
	// log.Println(e, d)
	// log.Println(count)
	if e {
		fmt.Println("Impossible")
	} else {
		for i := 0; i < 13; i++ {
			if d {
				switch {
				case count[i] == 2:
					continue
				case count[i] == 1:
					continue
				case count[i] == 0:
					fmt.Println(a[i])
				}
			} else {
				fmt.Println(a[i])
			}
		}
	}
}