Maximum XOR of two numbers

You are given $N$ numbers. Write a program that finds the two numbers whose XOR is the largest.

That is, among $A_1, A_2, \dots, A_N$, find the largest value of $A_i \oplus A_j$ over all index pairs with $i \neq j$.

The first line contains $N$ ($2 \le N \le 100{,}000$).

The second line contains $N$ numbers. Every number given in the input is a non-negative integer no greater than $1{,}000{,}000{,}000$.

Print the XOR of the two numbers whose XOR is the largest on the first line.