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

class Main {

    public static void main(String[] args) {

        Pattern upperCase = Pattern.compile("[A-Z]");
        Pattern lowerCase = Pattern.compile("[a-z]");
        Scanner sc = new Scanner(System.in);
        String input = sc.nextLine();

        Matcher upperMatcher = upperCase.matcher(input);
        Matcher lowerMatcher = lowerCase.matcher(input);

        if(upperMatcher.find()){
            System.out.println("A");
        }else if(lowerMatcher.find()){
            System.out.println("a");
        }
        sc.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