real analysis - Example of function $f:mathbb Rto mathbb R$ which is differentible and bijective but its inverse is not differentible.

Example of function $f:\mathbb R\to \mathbb R$ which is differentible and bijective but its inverse is not differentible.

First of all do not know is above is true as for inverse function to be not differentible , there exist some point at which $f'(x)=0$ which is not possible due to bijective ness .

Where I am missing ?

Any Help will be appereciated