program mandelbrot_simple
      implicit none
      complex c,z_ini,z
      integer pgopen,i,j,k,isymbol,n_gen
      real c_x_min,c_x_max,c_y_min,c_y_max,c_x,c_y,abs_z

      isymbol = -1

      write (*,*) 'The program plot Mandelbrot set in a simple way.'
      write (*,*)
      z_ini = (0.0,0.0)

      if ( pgopen('/xwin') .le. 0 ) stop
      call pgpap(5.0,1.0)

      write (*,*) 'What is the numer of iteration for the mapping ?'
      read (*,*) n_gen

      c_x_min = -2.0
      c_x_max =  0.5
      c_y_min = -1.25
      c_y_max =  1.25

      call pgenv(c_x_min, c_x_max, c_y_min, c_y_max, 1, 0)

      do j=1,500
        c_x = c_x_min + j*(c_x_max-c_x_min)/500
        call pgbbuf
        do k=1,500
          c_y = c_y_min + k*(c_y_max-c_y_min)/500
          c = (1.0,0.0)*c_x + (0.0,1.0)*c_y
          z = z_ini
          do i=1,n_gen
            z = z*z + c
            abs_z = conjg(z)*z
            if (abs_z.gt.10e+10) then
              call pgpt(1,c_x,c_y,isymbol)
              exit
            endif
          end do
        end do
        call pgebuf
      end do

      call pgclos
      end