#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000000009
#define INF 10000000
#define LLINF 2000000000000000000LL

#define SIZE 10001

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