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

using namespace std;

int main(){
    long long f0,f1,f2,n;
    
    scanf("%lld%lld%lld",&f0,&f1,&n);
    
    for(long long i=2;i<=n;i++){
        f2=f1^f0;
        f0=f1;
        f1=f2;
    }
    
    cout << f1 << endl;
    
    return 0;
}