Problem C
Reseto
The sieve of Eratosthenes is a famous algorithm to find all prime numbers up to $N$. The algorithm is:

Write down all integers between 2 and $N$, inclusive.

Find the smallest number not already crossed out and call it $P$; $P$ is prime.

Cross out $P$ and all its multiples that arenâ€™t already crossed out.

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.
Input
The integers $N$ and $K$ $(1 \leq K < N \leq 100\, 000)$.
Output
Output the $K$th number to be crossed out.
Sample Input 1  Sample Output 1 

7 3 
6 
Sample Input 2  Sample Output 2 

15 12 
7 
Sample Input 3  Sample Output 3 

10 7 
9 