int sum $=0$;

for$($int i $=$ N; i $>0$; i$--)\{$

if$($i $\%2==0)\{$

sum $+=1$;

$\}$

$\}$

$($Careful$,$ the if statement should be part of the BigO and will be different from sum$+=1.$ For sum$+=1$ consider when the if statement will be true and how many times that will occur for a given positive integer N$.)$