#include <bits/stdc++.h>

#define pout(n)  printf ("%d\n", n)

#define rep(i,a,n) for (int i = a;i < n;i++)
#define per(i,n,a) for (int i = n-1;i >= a;i--)

const int d4x[4] = {1, 0, -1, 0};
const int d4y[4] = {0, 1, 0, -1};
const int d8x[8] = { 1,1,0,-1,-1,-1,0,1 };
const int d8y[8] = { 0,1,1,1,0,-1,-1,-1 };

#define MAX_N (int)2e5+20
#define INF 1e12+20

typedef long long ll;
using namespace std;

ll f0,f1,n;
int main() {
    cin >> f0 >> f1 >> n;
    if(n%3 == 0) printf("%lld\n",f0);
    else if(n%3 == 1) printf("%lld\n",f1);
    else if(n%3 == 2) printf("%lld\n",f0^f1);
    return 0;
}