N=int(raw_input())
A=map(int,raw_input().split())
A.sort()
bit=1
while A[N-1]>=2*bit:
    bit*=2
area=[(0,N)]

ans=0

while bit>0:
    area1=[]
    area2=[]
    for s,t in area:
    #    print s,t
        if (A[s]&bit)==(A[t-1]&bit):
            area1.append((s,t))
        else:
            for k in range(s,t):
                if (A[k]&bit) > 0:
                    area2.append((s,k))
                    area2.append((k,t))
                    break
    #print
    if len(area1)>0:
        ans*=2
        area=area1
    else:
        ans*=2
        ans+=1
        area=area2
    bit/=2
print ans