Function $f$ is defined for the set of all natural number as follows:  $$f(x)=\begin{cases}\dfrac{x}{2},(\text{when }x\text{ is even}) \textbackslash\textbackslash{} x+1,(\text{when }x\text{ is odd}) \textbackslash\textbackslash{} \end{cases}$$.  For example: $$f(3)=3+1=4$$, $$f(2)=2\div 2=1$$.  What is the value of $$f(f(f(f(f(17)))))$$? 
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$$\textasciitilde\textasciitilde\textasciitilde\textasciitilde f\left( f\left( f\left( f\left( f\left( 17 \right) \right) \right) \right) \right)$$  $$=f\left( f\left( f\left( f\left( 18 \right) \right) \right) \right)$$  $$=f\left( f\left( f\left( 9 \right) \right) \right)$$  $$=f\left( f\left( 10 \right) \right)$$  $$=f\left( 5 \right)$$  $$=6$$． 