#include <bits/stdc++.h>
#define PB push_back
#define MP make_pair
#define REP(i,n) for (int i=0;i<(n);i++)
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define ALL(a) (a).begin(),(a).end()
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
const int INF=1e9;
ll rec(ll a,ll b){
      return a^b;
}
int main(){
      ll n,f[10];
      cin>>f[0]>>f[1]>>n;
      if(n%3==0)cout<<f[0]<<endl;
      else if(n%3==1)cout<<f[1]<<endl;
      else cout<<rec(f[0],f[1])<<endl;
}