#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  for(int i=0;i<(n);i++)
#define FORq(i, m, n) for(int i = (m);i <= (n);i++)
#define SCD(n) scanf("%d",&n)
#define SCD2(m,n) scanf("%d%d",&m,&n)
#define SCD3(m,n,k) scanf("%d%d%d",&m,&n,&k)
#define PB push_back
#define MP make_pair
#define ARSCD(A,N) REP(i,N){SCD(A[i]);}
#define ARSCD1(A,N) FORq(i,1,N){SCD(A[i]);}
#define PRINTD(n) printf("%d\n",n)
#define PRINTLLD(n) printf("%lld\n",n)
#define DEBUG printf("%s\n","debug")
#define fst first
#define snd second
using namespace std;
typedef pair<int,int> PII;
typedef vector<int> VI;
typedef long long ll;
//////////////////////////////////////////////////////
int main(){
	ll F0,F1,N;
	scanf("%lld %lld %lld",&F0,&F1,&N);
	ll b2,b1;
	
	b2 = F0; b1 = F1;
	
	for (ll i = 2; i <= N;i++){
		ll Fi = b2 ^ b1;
		b2 = b1;
		b1 = Fi;
	}
	
	PRINTLLD(b1);
	
	return 0;
}