import java.util.*;
import java.io.*;
class Main{
	public static void main(String[] args) {
	Scanner sc=new Scanner(System.in);
	String str= sc.nextLine();
	String str1=str.toUpperCase();
	if(str==str1)
	{
		System.out.println("A");
	}
	else
	{
		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