#include<stdio.h>

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

  scanf("%llu%llu%llu",&F0,&F1,&N);
  //printf("%llu %llu %llu\n",F0,F1,N);

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

  return 0;
}