def rec(x,i,mn):
    if i < 0: return mn
    res = mn
    xx = x | (1 << i)
    tmp = max(ai^xx for ai in a)
    if   tmp  < mn: res = min(res, rec(xx,i-1,tmp))
    elif tmp == mn: res = min(res, rec(xx,i-1,mn), rec(x,i-1,mn))
    else:           res = min(res, rec(x,i-1,mn))
    return res

N = int(raw_input())
a = map(int,raw_input().split())
mn = max(a)
print rec(0,30,mn)