#include <iostream>
#include <math.h>
#include <algorithm>
#include <functional>
#include <vector>
#include <typeinfo>
#include <climits>
#include <ctype.h>
#include <string>
#include <stack>
using namespace std;
#define FOR(i, a, n) for (int i = a; i < n; i++)
#define REP(i, n) for(int i = 0; i < n; i++)
struct omt{omt(){ios::sync_with_stdio(false);cin.tie(0);}}star;

int main(){
    vector<long long> v;
    REP(i, 2){
        long long tmp;
        cin >> tmp;
        v.push_back(tmp);
    }
    long long n;
    cin >> n;

    FOR(i, 2, n + 1){
        v.push_back(v[i - 2] ^ v[i - 1]);
    }
    cout << v[n] << endl;


    return 0;
}