import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.next();
        boolean lowercase = !s.equals(s.toLowerCase());
        boolean uppercase = !s.equals(s.toUpperCase());
        if (!lowercase) {
            System.out.println("a");
        }
        if (!uppercase) {
            System.out.println("A");
        }
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz