import math


def pop_count(k):
    count = 0
    for i in range(k.bit_length()):
        if k >> i & 1 == 1:
            count += 1
    return count


x = int(input())

if x != 0 and x != 1 and x != 2:
    for m in range(math.ceil(math.log2(x))+1):
        n = m ^ x
        if pop_count(n) == m:
            print(n)
            break
    else:
        print(-1)
else:
    if x == 2:
        print(-1)
    elif x == 1:
        print(3)
    else:
        print(1)