// No.1217 せしすせそ
package main

import "fmt"

func main() {
	const base = "abcdefghijklmnopqrstuvwxyz"
	var s string
	fmt.Scan(&s)
	for i, r := range base {
		if string(r) != string(s[i]) {
			fmt.Println(string(r) + "to" + string(s[i]))
			break
		}
	}
}