import java.util.Scanner;
import java.util.regex.Pattern;

public class Main {
    public static void main(String[] args) {
    	Scanner scanner = new Scanner(System.in);
        String a = scanner.next();
        if(Pattern.matches("[A-Z]", a)) {
        	System.out.println("A");
        }else if(Pattern.matches("[a-z]", a)) {
        	System.out.println("a");
        }
        scanner.close();
    }
}
/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