The atoi$()$ function takes a string $($which represents an integer$)$ as an argument and returns its value.

Consider the following two recursive implementations atoiR$1()$ and atoiR$2().$

def atoiR$1($string$,$ num$)$:

if $($len$($string$)=0)$:

return $0$

if len$($string$)=1$ :

return int string