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
flg = False
for i in range(ma+1):
    if flg:
        break
    s = set()
    for j in range(n):
        s.add(lis[j][i])
    if len(s) == 1:
        if s == {0}:
            ans += 2**i
            flg = True
        
print(ans)