program main

!*****************************************************************************80
!
!! MAIN is the main program for SEARCH.
!
!  Licensing:
!
!    This code is distributed under the GNU LGPL license.
!
!  Modified:
!
!    22 October 2012
!
!  Author:
!
!    John Burkardt
!
  implicit none

  integer ( kind = 4 ) a
  integer ( kind = 4 ) b
  integer ( kind = 4 ) c
  integer ( kind = 4 ) f
  integer ( kind = 4 ) fj
  integer ( kind = 4 ), parameter :: i4_huge = 2147483647
  integer ( kind = 4 ) j
  real ( kind = 8 ) wtime

  a = 1
  b = i4_huge
  c = 45

  call timestamp ( )
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'SEARCH:'
  write ( *, '(a)' ) '  FORTRAN90 version'
  write ( *, '(a)' ) '  Search the integers from A to B'
  write ( *, '(a)' ) '  for a value J such that F(J) = C.'
  write ( *, '(a)' ) ' '
  write ( *, '(a,i12)' ) '  A           = ', a
  write ( *, '(a,i12)' ) '  B           = ', b
  write ( *, '(a,i12)' ) '  C           = ', c

! wtime = ???

  call search ( a, b, c, j )

! wtime = ??? - wtime

  if ( j == -1 ) then
    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) '  No solution was found.'
  else
    write ( *, '(a)' ) ' '
    write ( *, '(a,i12)' ) '  Found     J = ', j
    write ( *, '(a,i12)' ) '  Verify F(J) = ', f ( j )
  end if

  write ( *, '(a,g14.6)' ) '  Elapsed time is ', wtime
!
!  Terminate.
!
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'SEARCH:'
  write ( *, '(a)' ) '  Normal end of execution.'

  stop
end
subroutine search ( a, b, c, j )

!*****************************************************************************80
!
!! SEARCH searches integers in [A,B] for a J so that F(J) = C.
!
!  Licensing:
!
!    This code is distributed under the GNU LGPL license.
!
!  Modified:
!
!    22 October 2012
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    Input, integer ( kind = 4 ) A, B, the search range.
!
!    Input, integer ( kind = 4 ) C, the desired function value.
!
!    Output, integer ( kind = 4 ) J, the computed solution, or -1
!    if no solution was found.
!
  implicit none

  integer ( kind = 4 ) a
  integer ( kind = 4 ) b
  integer ( kind = 4 ) c
  integer ( kind = 4 ) f
  integer ( kind = 4 ) fi
  integer ( kind = 4 ) i
  integer ( kind = 4 ) j

  j = -1

  do i = a, b

    fi = f ( i )

    if ( fi == c ) then
      j = i
      exit
    end if

  end do

  return
end
function f ( i )

!*****************************************************************************80
!
!! F is the function we are analyzing.
!
!  Licensing:
!
!    This code is distributed under the GNU LGPL license.
!
!  Modified:
!
!    22 October 2012
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    Input, integer ( kind = 4 ) I, the argument.
!
!    Input, integer ( kind = 4 ) F, the value.
!
  implicit none

  integer ( kind = 4 ) f
  integer ( kind = 4 ) i
  integer ( kind = 4 ), parameter :: i4_huge = 2147483647
  integer ( kind = 4 ) j
  integer ( kind = 4 ) k
  integer ( kind = 4 ) value

  value = i

  do j = 1, 5

    k = value / 127773

    value = 16807 * ( value - k * 127773 ) - k * 2836

    if ( value <= 0 ) then
      value = value + i4_huge
    end if

  end do

  f = value

  return
end