#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < n; i++) //[0,n)
#define srep(i,a,b) for(int i = a; i < b; i++) //[a,b)
#define all(A) (A).begin(),(A).end()
#define rall(A) (A).rbegin(),(A).rend()
#define pmt(A) next_permutation(A)
using namespace std;
using ll = long long;
using ull = unsigned long long;
using P = pair<ll,ll>;
using pq = priority_queue<ll,vector<ll>,greater<ll>>;
//smaller
const ll inf = 8e18;
const int iinf = (int)1e9;
const int mod9 = 998244353;
const int mod1 = 1000000007;
struct Edge {
    int to;
    ll cost;
    //int from;
};
bool compe(const Edge &e,const Edge &e2){ return e.cost < e2.cost; }
using Graph = vector<vector<int>>;
using EGraph = vector<Edge>;
using SGraph = vector<set<ll>>;
template <typename T>
int siz(T& a){ return (int)a.size(); }
double squa(double x){ return 1.0*x*x; }
double pi = acos(-1);
double chrad(int d){ return 1.0*d/180*pi; }
using namespace std;

int main(){
    ll f0,f1,n; cin >> f0 >> f1 >> n;
    if(n%3 == 0) cout << f0;
    else if(n%3 == 1) cout << f1;
    else cout << (f1^f0);
}