n = int(input())
a = list(map(int,input().split()))

lis = []
ma = 0
for i in range(n):
    num = a[i]
    li = []
    while num > 0:
        li.append(num%2)
        num //= 2
    l = len(li)
    ma = max(ma,l)
    add = 73-l
    for j in range(add):
        li.append(0)
    lis.append(li)
    
ans = 0
# print(lis)
for i in range(ma+1):
    if i == ma:
        if ans != 0:
            break
    flg = True
    for j in range(n):
        if lis[j][i] == 1:
            flg = False
            break
        
    if flg:
        ans += 2**i
    
        
print(ans)