def Perm(l):
    if(l > 0):
        for p in Perm(l - 1):
            for c in range(ord('A'), ord('Z')):
                yield chr(c) + p
            for c in range(ord('a'), ord('Z')):
                yield chr(c) + p
    else:
        yield ''

for k in Perm(3):
    print k