What would be the time complexity of the following code?

int i$,$ j$,$ k $=0$;

for $($i $=$ n $/2$; i $<=$ n; i$++)$

$\{$

for $($j $=2$; j $<=$ n; j $=$ j $+2)$

$\{$

k $=$ k $+$ n $/2$;

$\}$

$\}$

O$($n$)$

O$($n$2)$

O$(1)$

O$($n logn$)$