#include <stdio.h>

long int F0, F1, N;
long int fib(long int k)
{
  if (k == 1) return F1;
  else if (k == 0) return F0;
  else return fib(k-1) ^ fib(k-2);
}

int main(void)
{
  scanf("%ld %ld %ld", &F0, &F1, &N);
  printf("%ld\n", fib(N));

  return 0;
}