A1153. [COCI-2008_2009-contest2]#4 RESETO

The sieve of Eratosthenes is a famous algorithm to find all prime numbers up to N. The algorithm is:
1. Write down all integers between 2 and N, inclusive.
2. Find the smallest number not already crossed out and call it P; P is prime.
3. Cross out P and all its multiples that aren't already crossed out.
4. If not all numbers have been crossed out, go to step
2.
Write a program that, given N and K, find the K-th integer to be crossed out.

The integers N and K (2 ≤ K < N ≤ 1000).

Output the K-th number to be crossed out.

In the third example, we cross out, in order, the numbers 2, 4, 6, 8, 10, 3, 9, 5 and 7. The seventh
number is 9.