import math
import random
# import numpy as np

def gcd(x: int, y: int) -> int:
    if x < y: x, y = y, x
    while y > 0:
        x %= y
        x, y = y, x
    return x

# code here
n = int(input())
a = [*map(lambda x: int(x) if x != "-1" else 0, input().split())]

mask = 1
while mask < n:
    for i in range(n):
        if not i & mask and (i | mask) < n:
            a[i] += a[i | mask]
    mask <<= 1

for i in range(n):
    a[i] **= 2

mask = 1
while mask < n:
    for i in range(n):
        if not i & mask and (i | mask) < n:
            a[i] -= a[i | mask]
    mask <<= 1

ans = -1
for x in a:
    if x == 0: continue
    if ans == -1:
        ans = x
    else:
        ans = gcd(ans, abs(x))
print(ans)