N = int(input())
A = list(map(int,input().split()))
ans = [0]*73
m = 0
for i in range(N):
    a = A[i]
    for j in range(73):
        if (a>>j)&1:
            ans[j] = 1
            m = max(m,j)
res = 0
for i in range(m):
    res += (1-ans[i])*(2**i)
if res == 0:
    res = 2**(m+1)
print(res)