#include<stdio.h>
#include<algorithm>
using namespace std;
int main(){
	long long a,b,c;
	scanf("%lld%lld%lld",&a,&b,&c);
	if(c%3==0)printf("%lld\n",a);
	else if(c%3==1)printf("%lld\n",b);
	else printf("%lld\n",a^b);
}