Max XOR

Choose lo≤a<b≤hi such that a XOR b≤k and the XOR value is as large as possible; return the XOR value. The two integers must be different; if no feasible pair exists, this site outputs -1.

输入格式

One line containing lo hi k. Full source ranges: 1≤lo<hi≤10000, 1≤k≤10000.

输出格式

Output one integer, the answer.

样例 1

输入：

3 5 6

输出：

6

样例 2

输入：

1 2 1

输出：

-1

样例 3

输入：

1 4 7

输出：

7

样例说明

The examples give 6, -1 and 7 respectively.