module para
  implicit none
  integer :: i
  integer,parameter :: N = 501
  real(8),parameter :: x0 = 0.d0, &
                     & xN = 20.d0, &
                     & y0 = 0.1d0
  real(8) :: h
end module para
!*********************************************************************
program rogi2
  use para
  implicit none
  real(8),dimension(N) :: x,y
  
  call calc_nexty(x,y)
  
  stop
end program rogi2
!*********************************************************************
subroutine calc_nexty(x,y)
  use para
  implicit none
  real(8),dimension(N) :: x,y
  
!/////calculate parameter
  h = (xN-x0)/dble(N-1)
!/////inicialize & boundary condition
  y(:) = 0.d0
  x(:) = 0.d0
  y(1) = y0
  
  do i = 2,N
    y(i) = y(i-1)+h*(y(i-1)-y(i-1)*y(i-1))
  end do
  
!/////output result
  do i = 1,N
    write(*,*)'i=',i,'y=',y(i)
  end do
  
  return
  
end subroutine calc_nexty