Using Big Oh notation, what is the tightest upper bound for the running time of the below function fun?

def fun$($n$)$: # n is a positive integer

count $=0$

i $=$ n

while i $>0$:

j $=0$

while j $<$ i:

count $+=1$

j $+=1$

i $//=2$ # Integer division rounds down

return count

Group of answer choices

O$($n$^2)$

Unbounded

O$($n log n$)$

O$($log n$)$

O$($n$)$