číslo kroku

A_{1} = (4.98, -1.38)
B = (16.86, -1.24)
f = Line(A_{1}, B)
A = (8.08, 2.42)
c = Parabola(A, f)
n = 0 (slider from 0 to 1, step 1)
S = Point(c)
d = Circle(S, A)