X = int(input())
def popcount(x):
    ans = 0
    while x > 0:
        if x % 2:
            ans += 1
        x //= 2
    return ans

for M in range(1, 70):
    N = X ^ M
    if N == 0:
        continue
    if popcount(N) == M:
        print(N)
        exit()
print(-1)