N = int(raw_input())
a = map(int,raw_input().split())
x = (1 << 31)-1
mn = max(ai^x for ai in a)
for i in xrange(30,-1,-1):
    xx = x ^ (1 << i)
    if max(ai^xx for ai in a) < mn:
        mn = max(ai^xx for ai in a)
        x = xx
print mn