import java.util.*;
 
public class Main {
    public static void main(String args[] ) throws Exception {
        Scanner sc = new Scanner(System.in);
        String[] answer = {"y", "u", "k", "i", "c", "o", "d", "e", "r"};
        String input = sc.next();
		for (int i = 0 ; i < 9 ; i++) {
			if (input.indexOf(answer[i]) == -1) {
				System.out.println(answer[i]);
				break;
			}
		}
    }
}