#include <bits/stdc++.h>
typedef  long long ll;
#define INF 1000000000
using namespace std;
#define N 1000000
#define MOD 1000000007
int main(void){
    ll a,b,n;
    cin>>a>>b>>n;
    ll f[3];
    f[0]=a;f[1]=b;
    f[2]=(f[0]^f[1]);
    cout<<f[n%3]<<endl;
}