#include <stdio.h>


int main(void){
	long long int	f0,f1,n;

	scanf("%lld %lld %lld",&f0,&f1,&n);

	switch(n%3){
		case 0:	printf("%lld\n",f0);	break;
		case 1:	printf("%lld\n",f1);	break;
		case 2:	printf("%lld\n",f0^f1);	break;
	}
	return 0;
}