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

def main():
    if input().isupper():
        print('A')
    else:
        print('a')

if __name__ == '__main__':
    main()

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

def main():
    if input().isupper():
        print('A')
    else:
        print('a')

if __name__ == '__main__':
    main()

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