Let $s(n,k)$ denote the unsigned Stirling numbers of the first kind. Prove that $$s(n, n-1) = {n\choose2} $$
-I am new to Stirling numbers, and looked up some definitions regarding it. I know that they count the number of permutations of n elements with k disjoint cycles. Although I am unsure of how to prove this and what kind of proof method to use.