Problem: You are given two integers n and k. Find k-th smallest divisor of n, or report that it doesn't exist.
Divisor of n is any such natural number, that n can be divided by it without remainder.
Input Format: The first line contains two integers n and k (1 ≤ n ≤ 1015, 1 ≤ k ≤ 109).
Output Format: If n has less than k divisors, output -1.
Otherwise, output the k-th smallest divisor of n.
Note: In the first example, number 4 has three divisors: 1, 2 and 4. The second one is 2.
In the second example, number 5 has only two divisors: 1 and 5. The third divisor doesn't exist, so the answer is -1.