#include <stdio.h>

int main() {
  long long f0, f1, n;
  scanf("%lld %lld %lld", &f0, &f1, &n);
  int rem=n%3;
  long long arr[3]={f0, f1, f0^f1};

  printf("%lld\n", arr[rem]);
  return 0;
}