#include<stdio.h>

int main(void){
	unsigned long long int a,b,n;
	scanf("%llu%llu%llu",&a,&b,&n);
	if(n%3 == 0){printf("%llu\n",a);}
	if(n%3 == 1){printf("%llu\n",b);}
	if(n%3 == 2){printf("%llu\n",a^b);}
	return 0;
}