#include int main(void){ long long F0, F1, F2, N; long long k = 2; scanf("%lld %lld %lld", &F0, &F1, &N); if(N==0){ printf("%lld\n", F0); }else if(N==1){ printf("%lld\n", F1); }else{ while(k<=N){ F2 = F0 ^ F1; F0 = F1; F1 = F2; k++; } printf("%lld\n", F2); } return 0; }