#include <bits/stdc++.h>
using namespace std;

// 基本テンプレート
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define MAT(type, c, m, n) vector<vector<type>> c(m, vector<type>(n));for(auto& r:c)for(auto& i:r)cin>>i;
#define REP(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define RREP(i,a,n) for(int i=(a); i>n; --i)
#define perm(c) sort(all(c));for(bool c##p=1;c##p;c##p=next_permutation(all(c)))
#define PB push_back
#define EM emplace
#define EB emplace_back
#define BI back_inserter
#define MP make_pair
#define cauto const auto&
#define UNIQUE(v) v.erase( unique(ALL(v)), v.end() );
#define len(x) ((int)(x).size())

// 型
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<string, string> pss;
typedef pair<string, int> psi;
typedef pair<int, string> pis;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long> vl;
typedef vector<long long> vll;
typedef vector<string> vs;



// Effective std
template<typename C> void remove(vector<C>& c, unsigned int index) { c.erase(c.begin()+index); }
template<typename T> inline bool chmin(T &a, const T &b){if (b < a) {a = b; return true;} return false; }
template<typename T> inline bool chmax(T &a, const T &b){if (a < b) {a = b; return true;} return false; }
inline void split(const string &s, char c, vector<int>& v) {stringstream ss(s);string bf; while(getline(ss, bf, c)) v.push_back(stoi(bf));}
inline void split(const string &s, char c, vector<string>& v) {stringstream ss(s);string bf; while(getline(ss, bf, c)) v.push_back(bf);}



// 定数
#define MOD 1e9+7
#define PI acos(-1.0)
constexpr int EPS = (1e-9);
constexpr int INF = 100000000;



int main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	cout << fixed << setprecision(15);

	ll f0, f1, n; cin >> f0 >> f1 >> n;

	if (n % 3 == 0) P(f0);
	else if (n % 3 == 1) P(f1);
	else P(f0 ^ f1);

    return 0;
}