$```$

Given the following code snippet, identify the basic blocks,

construct a control flow graph $($CFG$).$

#include

unsigned long long factorial$($int n$)\{$

if $($n$<mn>0</mn><mi>)</mi><mtext></mtext><mi>\{</mi>$

printf$("$Factorial is not defined for negative

numbers.

$")$;

return $0$; $\}$

if $($n $==0|$n$==1)\{$

return $1$; $\}$

return n $*$ factorial$($n$-1)$;

$\}$

int getValidInput$()\{$

int num;

while $(1)\{$

printf$("$Enter a non$-$negative integer: $")$;

if $($scanf$("\%$d$",$ &num$)!=1||$ num $<mtext></mtext><mn>0</mn><mi>)</mi><mtext></mtext><mi>\{</mi>$

printf$("$Invalid input. $")$;

while $($getchar$()!=\text{'}$

$\text{'})$; $\}$

else $\{$

break; $\}$

$\}$

return num;

$\}$

int main$()\{$

int number;

unsigned long long result;

number $=$ getValidInput$()$;

result $=$ factorial$($number$)$;

if $($result $!=0)\{$

printf$("$The factorial of $\%$d is $\%$llu.

$",$ number, result$)$;

$\}$

return $0$; $\}$

$```$