#include<stdio.h>
int main(){
    long long int x,y,n;
    scanf("%lld %lld %lld",&x,&y,&n);
    long long int z = x^y;
    if(n%3 == 0){
        printf("%lld",x);
    }else if(n%3 == 1){
        printf("%lld",y);
    }else{
        printf("%lld",z);
    }

    putchar('\n');
    return 0;
}