# import sys

# readline = sys.stdin.readline

# generator = (readline().strip() for _ in range(N))



# N, M = map(int, input().split())

# As = list(map(int, input().split()))

# queries = (input() for _ in range(N))





def solve():

    alpha = eval(input())



    if alpha.upper() == alpha:

        return 'A'



    return 'a'





def main():

    print((solve()))





if __name__ == "__main__":

    main()

def solve():

    letter = eval(input())



    answer = 'A' if letter.upper() == letter else 'a'



    return answer





def main():

    print((solve()))





if __name__ == "__main__":

    main()

# import sys
# readline = sys.stdin.readline
# generator = (readline().strip() for _ in range(N))
# N, M = map(int, input().split())
# As = list(map(int, input().split()))
# queries = (input() for _ in range(N))
def solve():
    alpha = eval(input())
    if alpha.upper() == alpha:
        return "A"
    return "a"


def main():
    print((solve()))


if __name__ == "__main__":
    main()

def solve():
    letter = eval(input())
    answer = "A" if letter.upper() == letter else "a"
    return answer


def main():
    print((solve()))


if __name__ == "__main__":
    main()

-# import sys -# readline = sys.stdin.readline -# generator = (readline().strip() for _ in range(N)) -# N, M = map(int, input().split()) -# As = list(map(int, input().split())) -# queries = (input() for _ in range(N)) -    alpha = eval(input()) -    if alpha.upper() == alpha: -        return "A" -    return "a" +    letter = eval(input()) +    answer = "A" if letter.upper() == letter else "a" +    return answer