#include<stdio.h>

int main(void){
  unsigned long long F0,F1,N,ans=0;
  unsigned long long i,j,k;

  scanf("%Lu%Lu%Lu",&F0,&F1,&N);

  for(i=0;i<64;i++){
    j=(F0>>i)&1;
    k=(F1>>i)&1;
    if(j)
      ans+=(k?(N%3!=2):(N%3!=1))<<i;
    else
      ans+=(k?(N%3!=0):0)<<i;
  }
  printf("%llu\n",ans);

  return 0;
}