def ans(n, k):
    # print(n, k)
    # print(2**n, 2**k)
    if n < k:
        xn = 0
    else:
        xn = 2**(n-k)
    return xn

if __name__ == '__main__':
    n, k = map(int, input().split())
    print(ans(n, k))