program main
  implicit none
  integer :: n =10
  interface 
     function fib(n)
       integer, intent(in) :: n 
       integer :: fib
     end function fib
  end interface
  
!  Open parallel region and pay attention to how many threads should call the following instruction
  print *, fib(n)

end program main

recursive function fib (n)  result (fnum) 
  integer, intent(in)  :: n
  integer :: i,j
  integer :: fnum
  if (n<2) then 
     fnum = n
  else
! use task construct here, decide what is shared or firstprivate
     i= fib(n-1)
! use task construct here, decide what is shared or firstprivate
     j= fib(n-2)
! use task construct here, is sincronization necessary? 
     fnum = i+j
  endif
end function fib