#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
#include<sstream>
#include<iterator>
using namespace std;
typedef  long long int lint;
typedef pair<int, int> IP;
typedef pair<lint, lint> LLP;
typedef pair<char, char>CP;
#define rep(i, n) for (int i = 0; i < n; i++)
#define repr(i, n) for (int i = n; i >= 0; i--)
#define sort(v) sort((v).begin(), (v).end())
#define reverse(v) reverse((v).begin(), (v).end())
#define upper(v,hoge) upper_bound(v.begin(),v.end(),hoge)
#define lower(v,hoge) lower_bound(v.begin(),v.end(),hoge)
#define llower(v,hoge) *lower_bound(v.begin(), v.end(), hoge)
#define lupper(v,hoge) *upper_bound(v.begin(), v.end(), hoge)

string ten_to_two(lint N) {
	//10進数から2進数
	string ans;
	while (1) {
		ans.push_back(char('0' + N % 2));
		N /= 2;
		if (N == 0) {
			break;
		}
	}
	reverse(ans);
	return ans;
}

lint power(lint A, lint B) {
	lint ans = 1;
	rep(i, B) {
		ans *= A;
	}
	return ans;
}

int main() {
	lint F0, F1, N;
	cin >> F0 >> F1 >> N;
	string S0 = ten_to_two(F0);
	string S1 = ten_to_two(F1);
	reverse(S0);
	reverse(S1);
	while (1) {
		S0.push_back('0');
		if (S0.size() == 50) {
			break;
		}
	}
	while (1) {
		S1.push_back('0');
		if (S1.size() == 50) {
			break;
		}
	}
	reverse(S0);
	reverse(S1);
	vector<char>A(50);
	rep(i, 50) {
		if (S0[i] == '0' && S1[i] == '0') {
			if (N % 3 == 0) {
				A[i] = '0';
			}
			else if (N % 3 == 1) {
				A[i] = '0';
			}
			else if (N % 3 == 2) {
				A[i] = '0';
			}
		}
		else if (S0[i] == '0' && S1[i] == '1') {
			if (N % 3 == 0) {
				A[i] = '0';
			}
			else if (N % 3 == 1) {
				A[i] = '1';
			}
			else if (N % 3 == 2) {
				A[i] = '1';
			}
		}
		else if (S0[i] == '1' && S1[i] == '0') {
			if (N % 3 == 0) {
				A[i] = '1';
			}
			else if (N % 3 == 1) {
				A[i] = '0';
			}
			else if (N % 3 == 2) {
				A[i] = '1';
			}
		}
		else if (S0[i] == '1' && S1[i] == '1') {
			if (N % 3 == 0) {
				A[i] = '1';
			}
			else if (N % 3 == 1) {
				A[i] = '1';
			}
			else if (N % 3 == 2) {
				A[i] = '0';
			}
		}
	}
	reverse(A);
	lint ans = 0;
	rep(i, 50) {
		ans += lint(A[i]-'0') * power(2, i);
	}
	cout << ans << endl;
}