cnt = [0] * 50

n = int(input())
A = list(map(int, input().split()))
max_j = 0
for a in A:
    for j in range(50):
        cnt[j] += a & 1
        a //= 2
        if a == 0:
            max_j = max(max_j, j)
            break

ans = max(A)
for j in range(max_j + 1):
    if cnt[j] == n:
        ans -= 2**j

print(ans)