Least Period

The smallest $n$ for which a point $x_0$ is a Periodic Point of a function $f$ so that $f^n(x_0)=x_0$. For example, for the Function $f(x)= -x$, all points $x$ have period 2 (including $x=0$). However, $x=0$ has a least period of 1. The analogous concept exists for a Periodic Sequence, but not for a Periodic Function. The least period is also called the Exact Period.