Recall that writing a function $f\in S_4$ in disjoint cycle form amounts to writing it as
$f=(1,4)(2,3)$, for example. If, for instance $4$ is a fixed point. That is, $f(4)=4$, and we have $f(1)=2, f(2)=3, f(3)=1$, then we write $f=(1,2,3)$.
How do we notate a function that is only fixed points? For example $f(x)=x, \forall x\in${$1,2,3,4$}.