import java.util.*;

public class Main {
    public static void main(String args[]){
        Scanner stdIn = new Scanner(System.in);
        String s = stdIn.next();
        String ss = s.toUpperCase();
        //boolean flag = true;
        
        if(s.equals(ss)){
            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