N=int(input())
A=list(map(int, input().split()))
A0=A[:]
M=max(A)
L=M.bit_length()

dp=[[] for _ in range(L+1)]

dp[0]=A

for i in range(L)[::-1]:
    for cnt in range(i+1):
        B=[]
        for a in dp[cnt]:
            B.append(a^(1<<i))
        temp=max(B)
        if not dp[cnt+1] or temp<=max(dp[cnt+1]):
            dp[cnt+1]=B

res=10**18
for B in dp[1:]:
    res=min(max(B),res)
print(res)