$1.[10$ points$]$ Write a function that finds the largest of three integers using pass$-$by$-$reference and return$-$by$-$reference. Your design can use the function we wrote to find the larger between two integers. Test your function in a program using the main function below. Name the program lab$31.$

int main $()$

$\{$

$//$ Declaration and initialization of three integers

int num$1,$ num$2,$ num$3$ ;

cout$<<$"Input three numbers:"$<>$num$1>>$num$2>>$num$3$;

$//$ Finding and printing the largest integers

cout $<<$ "Largest of the three integers is: $"$;

cout $<<$ largest $(\_\_\_\_,\_\_\_\_\_\_,\_\_\_\_\_)$; $//$You need to fill in the blanks

return $0$;

$\}$