import sys

def input(): return sys.stdin.readline().strip()



def resolve():

    s=eval(input())

    alphabets=list(chr(ord('a')+i) for i in range(26))

    if s in alphabets:

        print('a')

    else:

        print('A')

resolve()
import sys

def input(): return sys.stdin.readline().strip()



def resolve():

    s=eval(input())

    if s.lower()==s:

        print('a')

    else:

        print('A')

resolve()
import sys


def input():
    return sys.stdin.readline().strip()


def resolve():
    s = eval(input())
    alphabets = list(chr(ord("a") + i) for i in range(26))
    if s in alphabets:
        print("a")
    else:
        print("A")


resolve()

import sys


def input():
    return sys.stdin.readline().strip()


def resolve():
    s = eval(input())
    if s.lower() == s:
        print("a")
    else:
        print("A")


resolve()

-    alphabets = list(chr(ord("a") + i) for i in range(26)) -    if s in alphabets: +    if s.lower() == s: