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Problem K
Salt
Given an array $a$ of length $n$, find the minimum nonnegative integer $s$ such that for some $L \geq 0$, $a_i = (L + i) \operatorname {XOR} s$ for all $ 0 \leq i \leq n-1$. The existence of at least one such $s$ is guaranteed by the input.
Input
The input consists of 2 lines, the first line containing a single integer $n$ ($1 \leq n \leq 10^6$), and the second line containing $n$ space-separated integers $a_0, a_1, \dots , a_{n - 1}$ ($0 \leq a_i \leq 10^{18}$).
Output
Output a single line, containing the integer $s$.
| Sample Input 1 | Sample Output 1 |
|---|---|
3 6 7 0 |
4 |
