



def resolve():

    import sys

    input = sys.stdin.readline

    n = str(input().rstrip())



    if n.isupper():

        print("A")

    else:

        print("a")



    # a_set = set()

    # duplicate = set()

    # for a in input().rstrip().split():

    #     a = int(a)

    #     if a in a_set:

    #         duplicate.add(a)

    #     else:

    #         a_set.add(a)



    # a_list = list(a_set)

    # a_list.sort()



    # answer = 0

    # divisors = set()

    # for a in a_list:

    #     judge = True

    #     for divisor in divisors:

    #         if a % divisor == 0:

    #             judge = False

    #             break

    #     if judge:

    #         divisors.add(a)

    #         if a in duplicate:

    #             continue

    #         answer += 1



    # print(answer)





if __name__ == "__main__":

    resolve()





def resolve():

    import sys

    input = sys.stdin.readline

    n = input().rstrip()

    if n.islower():

        print("a")

    else:

        print("A")







if __name__ == "__main__":

    resolve()

def resolve():
    import sys

    input = sys.stdin.readline
    n = str(input().rstrip())
    if n.isupper():
        print("A")
    else:
        print("a")
    # a_set = set()
    # duplicate = set()
    # for a in input().rstrip().split():
    #     a = int(a)
    #     if a in a_set:
    #         duplicate.add(a)
    #     else:
    #         a_set.add(a)
    # a_list = list(a_set)
    # a_list.sort()
    # answer = 0
    # divisors = set()
    # for a in a_list:
    #     judge = True
    #     for divisor in divisors:
    #         if a % divisor == 0:
    #             judge = False
    #             break
    #     if judge:
    #         divisors.add(a)
    #         if a in duplicate:
    #             continue
    #         answer += 1
    # print(answer)


if __name__ == "__main__":
    resolve()

def resolve():
    import sys

    input = sys.stdin.readline
    n = input().rstrip()
    if n.islower():
        print("a")
    else:
        print("A")


if __name__ == "__main__":
    resolve()

-    n = str(input().rstrip()) -    if n.isupper(): +    n = input().rstrip() +    if n.islower(): +        print("a") +    else: -    else: -        print("a") -    # a_set = set() -    # duplicate = set() -    # for a in input().rstrip().split(): -    #     a = int(a) -    #     if a in a_set: -    #         duplicate.add(a) -    #     else: -    #         a_set.add(a) -    # a_list = list(a_set) -    # a_list.sort() -    # answer = 0 -    # divisors = set() -    # for a in a_list: -    #     judge = True -    #     for divisor in divisors: -    #         if a % divisor == 0: -    #             judge = False -    #             break -    #     if judge: -    #         divisors.add(a) -    #         if a in duplicate: -    #             continue -    #         answer += 1 -    # print(answer)