(a) A snark starts at 0 on a number line. Every second it teleports a distance of N along the number line, where N is an unknown positive integer.

Every second, you choose a point on the number line. If you choose the snark's current location, you have caught it.

Can you come up with a strategy that will eventually catch the snark?

(b) As above, but now the snark starts at an unknown point S on the number line, where S is a positive integer.