use std::io::*;
use std::str::*;

const MOD: i32 = 1000000007;

fn read<T: FromStr>() -> Option<T> {
    let stdin = stdin();
    let s = stdin
        .bytes()
        .map(|c| c.unwrap() as char)
        .take_while(|c| !c.is_whitespace())
        .collect::<String>();
    s.parse::<T>().ok()
}

fn main() {
    let mut f0: u64 = read().unwrap();
    let mut f1: u64 = read().unwrap();
    let mut n: u64 = read().unwrap();
    if n == 1 {
        println!("{}", f1);
        return;
    }
    if n == 0 {
        println!("{}", f0);
        return;
    }

    if n == 2 {
        println!("{}", (f0 ^ f1));
        return;
    }
    n = (n - 2) % 3;

    let mut f2: u64 = 0;
    for _ in 0..n + 1 {
        f2 = f0 ^ f1;
        f0 = f1;
        f1 = f2;
        //        println!("{} {} {}", f0, f1, f2);
    }

    println!("{}", f2);
}