import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		sc.close();

		String t = "abcdefghijklmnopqrstuvwxyz";
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				System.out.println(t.charAt(i) + "to" + s.charAt(i));
				return;
			}
		}
	}
}