import java.util.*;
public class Main {
	public static void main(String[] args){
	   Scanner sc = new Scanner(System.in);
	   String str = sc.next();
      
      if(str.length()==1 && !str.equals("@")){
 
      if(Character.isUpperCase(str.charAt(0))){
      	str = "A";
      }else{
        str = "a";
      }
		// 出力
		System.out.println(str);     
	}
        
      }
}
/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