In the following code fragment, how many recursive calls are done when mystery$(5)$ is called and what is the return value?

int mystery$($int n$)$

$\{$

if $($n$<=0)$ return $0$;

if $($n$==1||$ n$==2)$ return $1$;

return n $+$ mystery$($n$-2)+$ mystery$($n$-1)$;

$\}$