#include <cstdio>

int main(void) {
  long long f0, f1, f2, n;
  scanf("%lld %lld %lld", &f0, &f1, &n);
  f2 = f0 ^ f1;

  switch (n % 3) {
    case 0:
      printf("%lld\n", f0);
      break;
    case 1:
      printf("%lld\n", f1);
      break;
    case 2:
      printf("%lld\n", f2);
      break;
  }

  return 0;
}