Permutations And Combinations

Let $r, l$ be two integers such that $r \geq l \geq 3$. What is the total number of functions
$f : \{1, 2, \ldots, r\} \rightarrow \{1, 2, \ldots, r\}$
such that $f(1), f(2), \ldots, f(l)$ are all distinct?