walls

uses
  crt;

var
  a, b, c: integer;

begin
  textbackground(white);
  clrscr;
  textcolor(red);
  for b := 1 to 1000 do
  begin
    a := random(10);
    if a > 7 then write('[]')
    else write('  ');
  end;
  readln;
end.