import scala.math._

object Main {
  def main(args: Array[String]) {
    val sc = new java.util.Scanner(System.in)
    val f0, f1, n = sc.nextLong

    val m = (n % 3).toInt
    val ans = Array(f0, f1, f0 ^ f1)(m)
    println(ans)
  }
}