program hello_world
  use omp_lib
  implicit none     
  integer :: n_threads, thread_id
  
!$omp parallel private(n_threads, thread_id)

  thread_id = omp_get_thread_num()
  print *, "Hello World from thread ", thread_id

  if (thread_id .eq. 0) then
      n_threads = omp_get_num_threads()
      print *, "Number of threads is ", n_threads
  end if

!$omp end parallel
  n_threads = omp_get_num_threads()
  print *, "Number of threads is ", n_threads
end program hello_world