Consider the C function foo and the binary tree shown.

typedef struct node $\{$

int val;

struct node $*$left$,*$right;

$\}$ node;

int cse$($node $*$p$)\{$

int retval;

if $($p $=$ NULL$)$

return $0$;

else $\{$

retval $=$ p$->$val $+$ foo$($p$->$left$)+$ foo$($p$->$right$)$;

printf$("\%$d $",$ retval$)$;

return retval;

$\}$

$\}$

When foo is called with a pointer to the root node output $?$