program small_pgm
! Everything from here to the "end program" statement is 
! a part of the main program.

! .. Implicit None Statement ..
  implicit none

! .. Local Scalars ..
  real :: n, x

! .. Executable Statements ..
  write (*,'(1x,a)',advance='NO') 'Number >1: '
  read *, n
  call number_of_primes
  print *, 'Approximately ', x, ' primes less than', n

contains
  subroutine number_of_primes
! .. Implicit None Statement ..
    implicit none

! .. Intrinsic Functions ..
    intrinsic LOG

! .. Executable Statements ..
    x = n/LOG(n)
  end subroutine number_of_primes
end program small_pgm