I think its quite simple but I keep getting W.A. .
I solve it by using the fact that any point Q satisfies
(Q-C).N = 0, I substitute M with Q and get quadratic
equation except in the case when Nz = 0. I solve it and
verify for the roots if the distance is < r.
I verified my computations at least 3 times. Here are a, b,
c for the quad equation:
- 5 * nz,
vx * nx + vy * ny + vz * nz,
nx * (sx - cx) + ny * (sy - cy) + nz * (sz - cz).
I hope I didn't f#$!ed up the computations again, because I
usualy do it.
Please help!

If the dart is on the plane at the beginning ,
u will also print it.

> If the dart is on the plane at the beginning ,
> u will also print it.