Find the number of functions f:{1,2,3,4,5}→{1,2,3,4,5}f: \{1, 2, 3, 4, 5\} \to \{1, 2, 3, 4, 5\}f:{1,2,3,4,5}→{1,2,3,4,5} such that f(f(x))=xf(f(x)) = xf(f(x))=x for all xxx.
26
31
120
15