#include <bits/stdc++.h>

using namespace std;

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
typedef long long ll;

const double EPS = 1e-8;
const int INF = 1e9;
const int MOD = 1e9+7;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

int main(void) {
	ll f0,f1,n;
	cin >> f0 >> f1 >> n;

	ll f2 = f0 ^ f1;
	if(n%3==0)
		cout << f0 << endl;
	else if(n%3==1)
		cout << f1 << endl;
	else
		cout << f2 << endl;
	
	

	return 0;
}