integer(kind=8)::F0,F1,N,modn,res
  read *, F0, F1, N
  modn=MOD(N,3)
  select case (modn)
  case(0)
     res = F0
  case(1)
     res = F1
  case(2)
     res = IEOR(F0,F1)
  end select
  print '(i0)',res
end program