import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		
		char a = scan.next().charAt(0);
		
		if (Character.isUpperCase(a)) {
			System.out.println("A");	// 大文字
		}
		else {
			System.out.println("a");	// 小文字
		}
		
		scan.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