#include <stdio.h>

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