import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    char ch = sc.next().toCharArray()[0];
    char a = 'a';
    Set<Character> set = new HashSet<>();
    for(int i=0;i<26;i++){
      set.add((char)(a+i));
    }
    if(set.contains(ch)){
      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