#include <stdio.h>

int main(void){
    long long F0, F1, F2, N;
    scanf("%lld %lld %lld", &F0, &F1, &N);

    if(N%3 == 0){
    	printf("%lld\n", F0);
    }else if(N%3 == 1){
    	printf("%lld\n", F1);
    }else{
    	F2 = F0 ^ F1;
    	printf("%lld\n", F2);
    }
    return 0;
}