Kth smallest element in a row$-$wise and column$-$wise sorted $2$D array: $(1$ byte$)$

In C$.$

Given an n x n matrix, where every row and column is sorted in non$-$decreasing order.

Find the kth smallest element in the given $2$D array.

For example:

Input:

k $=3$

array:

$10,20,30,40$

$15,25,35,45$

$24,29,37,48$

$32,33,39,50$

Output: $20$