#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;


int main()
{
  ll f[3],N;
  cin >> f[0] >> f[1] >> N;
  f[2] = f[0] ^ f[1];
  cout << f[N%3] << endl;
  return 0;
}