def power_two(num):
    while num > 1:
        if  num % 2 != 0:
            return False
        else:
            num /= 2

    return True

def not_power_of_two(num):
    for i in range(num):
        a = i
        b = N - i

        if power_two(a) or power_two(b):
            continue
        else:
            return min(a, b)

    return -1

if __name__ =='__main__':
    N = int(input())
    print(not_power_of_two(N))