#include <iostream>
#include <iomanip>

#include <algorithm>
#include <string>
/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////

int main(void){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout << fixed;//
	//cout << setprecision(7);//
	
	LL F0,F1,N;
	cin>>F0>>F1>>N;
	//[0,10^18]
	LL ans;
	if(N%3 == 0){
		ans = F0;
	}
	else if(N%3 == 1){
		ans = F1;
	}
	else if(N%3 == 2){
		ans = F1 ^ F0;
	}
	P(ans);
	return 0;
}