def aa(l,r,c):
    if r-l==1:
        return 0
    if c<0:
    	return 0
    m=l;d=1<<c
    res=1<<60
    while m<r and a[m]&d:
        m+=1
    if l<m:
        res=min(res,aa(l,m,c-1))
    if m<r:
        res=min(aa(m,r,c-1),res)
    if l<m<r:
    	res|=d
    return res


n=int(input())
a=list(map(int,input().split()))
a.sort(reverse=True)
print(aa(0,n,29))