def main():

    a = eval(input())

    if a in ['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']:

        print('A')

    else:

        print('a')



if __name__ == "__main__":

    main()

def main():

    s = eval(input())

    ko = [i for i in range(ord('a'),ord('z')+1)]

    if ord(s) in ko:

        print('a')

    else:

        print('A')



if __name__ == "__main__":

    main()

def main():
    a = eval(input())
    if a in [
        "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",
    ]:
        print("A")
    else:
        print("a")


if __name__ == "__main__":
    main()

def main():
    s = eval(input())
    ko = [i for i in range(ord("a"), ord("z") + 1)]
    if ord(s) in ko:
        print("a")
    else:
        print("A")


if __name__ == "__main__":
    main()

-    a = eval(input()) -    if a in [ -        "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", -    ]: +    s = eval(input()) +    ko = [i for i in range(ord("a"), ord("z") + 1)] +    if ord(s) in ko: +        print("a") +    else: -    else: -        print("a")