/*Source*/
import Lsystem;

size(8cm,0);
Lsystem Koch=Lsystem("+F+F+F+F+F",
                     new string[][]{{"F","F-F++F-F"}},
                     La=72);
Koch.iterate(4);
filldraw(Koch.paths()[0]&cycle, paleyellow, 1bp+black);
shipout(bbox(2mm, Fill(lightyellow)));