#include <stdio.h>
int main(void){
	long int N;
	long int F0,F1;
	long int Fn;
	
	scanf("%ld %ld %ld",&F0,&F1,&N);
	
	if(N == 0){
		Fn = F0;
	}else if(N == 1){
		Fn = F1;
	}else{
		for(int i = 2; i <= N; i++){
			Fn = F1 ^ F0;
			F0 = F1;
			F1 = Fn;
		}
	}
	
	printf("%ld\n",Fn);
	return 0;
}