import java.util.Scanner;

class Main{
	public static void main(String args[]){
      Scanner sc = new Scanner(System.in);
	        String str1 = sc.next();  
			String moji = str1.toUpperCase();
        	if(str1 == moji){
            	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