Find the Unique Number

Given an array of integers where every element appears exactly twice except for one, your task is to find that single unique number. This problem can be efficiently solved using the bitwise XOR operation, which has the property that \(a \oplus a = 0\) and \(a \oplus 0 = a\). Hence, by XOR-ing all the numbers, the duplicate numbers cancel out and only the unique number remains.

The input is provided via standard input (stdin) as a single line of space-separated integers, and your program should output the result to standard output (stdout).

inputFormat

A single line containing space-separated integers. It is guaranteed that every integer appears exactly twice except for one integer which appears only once.

outputFormat

Print the unique number that appears only once.## sample

2 3 4 2 3

4