package main

import "fmt"

func main() {
    var a, b, n int64
    fmt.Scan(&a, &b, &n)

    if n == 0 {
        fmt.Println(a)
    } else {
        for i := int64(2); i <= n; i++ {
            a, b = b, a ^ b
        }
        fmt.Println(b)
    }
}