N=int(input())
A=list(map(int, input().split()))
M=max(A)
L=M.bit_length()
for i in range(L)[::-1]:
    B=[]
    for a in A:
        B.append(a^(1<<i))
    temp=max(B)
    if temp<=M:
        M=temp
        A=B
print(M)