proc Draw_Triangle (X1, Y1, X2, Y2, X3, Y3, Colour : int)
    var XArray, YArray : array 1 .. 3 of int
    XArray (1) := X1
    YArray (1) := Y1
    XArray (2) := X2
    YArray (2) := Y2
    XArray (3) := X3
    YArray (3) := Y3
    drawfillpolygon (XArray, YArray, 3, Colour)
end Draw_Triangle

proc Sierpinski_Triangle (X1, Y1, X2, Y2, X3, Y3, Colour, Iterations : int)
    if Iterations > 0 then
        Draw_Triangle((X1+X2)div 2, (Y1+Y2)div 2, (X2+X3)div 2, (Y2+Y3)div 2, (X1+X3)div 2, (Y1+Y3)div 2, Colour)
        Sierpinski_Triangle (X1, Y1, (X1+X2)div 2, (Y1+Y2)div 2, (X1+X3)div 2, Y3, Colour, Iterations-1)
        Sierpinski_Triangle ((X1+X3)div 2, Y1, (X2+X3)div 2, (Y2+Y3)div 2, X3, Y3, Colour, Iterations-1)
        Sierpinski_Triangle ((X1+X2)div 2, (Y1+Y2)div 2, X2, Y2, (X2+X3)div 2, (Y2+Y3)div 2, Colour, Iterations-1)
    end if
end Sierpinski_Triangle

var Arrow : string(1)
var Iter, Max : int := 0

put "Seirpinski's Triangle\n"
put "Controls:"
put "Up arrow - one more deep"
put "Down arrow - one less deep"
put "Escape - quit\n"
put "Enter the triangle base length (0>L>1500): "..
get Max

View.Set("graphics:" + intstr(Max) + ";" + intstr(round(Max*sind(60))+1) + ",offscreenonly,nocursor")
loop
    cls
    Draw_Triangle      (0,0,Max div 2,round(Max*sind(60)),Max,0,black)
    Sierpinski_Triangle(0,0,Max div 2,round(Max*sind(60)),Max,0,red,Iter)
    View.Update
    getch(Arrow)
    if ord(Arrow) = 200 then
        Iter += 1
    elsif ord(Arrow) = 208 and Iter > 0 then
        Iter -= 1
    end if
    exit when ord(Arrow) = 27       
end loop

(0>L>1500)

max(minNumber, min (maxNumber, input))