import sys

sys.setrecursionlimit(10 ** 6)
def II(): return int(sys.stdin.readline())

def main():
    def g(x):
        if x==1:return 0
        if x==2:return 1
        ret=set()
        d2=x//2
        ret.add(g(d2)^g(x-d2))
        d3=(x+1)//3
        ret.add(g(x-d3*2))
        for res in range(3):
            if res not in ret:return res

    n=II()
    if g(n):print("A")
    else:print("B")

main()