#include <stdio.h>
#include <stdlib.h>

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

  if (N % 3 == 0 && (N - 1) % 3 == 0)
    printf("%d\n", 0);
  else if (N % 3 == 0)
    printf("%ld\n", F0);
  else if ((N - 1) % 3 == 0)
    printf("%ld\n", F1);
  else
    printf("%ld\n", F1 ^ F0);
  
  return 0;
}