CF762A k-th divisor

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.

The first line contains two integers $ n $ and $ k $ ( $ 1

If $ n $ has less than $ k $ divisors, output -1. Otherwise, output the $ k $ -th smallest divisor of $ n $ .

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.