import java.util.Scanner;
 
public class Main {
   public static void main(String[] args) {
       Scanner sc = new Scanner(System.in);
     
        //String[] ALFA = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
        //String[] alfa = {"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
        
        String S = sc.nextLine();
        
        //Sに大文字が含まれるとき
        if(S.toUpperCase() == S) { 
          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