import java.util.*;

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		String str=sc.next();
		String bs=str.toUpperCase();
		String ss=str.toLowerCase();
		if(str.equals(bs))
		{
			System.out.println("A");
		}
		else if(str.equals(ss))
		{
			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