The answer is $743.$ However, I do not understand why n $=3$ at the end.

#include

#include

int main $($int argc, char $*$argv$[])\{$

char$*$ str $=$ argv$[1]$;

char$*$ str$2=$ argv$[2]$;

const char ch $=\text{'}7\text{'}$;

char $*$p;

p $=$ strchr$($str$,$ ch$)$;

printf$("\%$c$",$ p$[1])$;

p $=$ strrchr$($str$,$ ch$)$;

printf$("\%$c$",$ p$[1])$;

int n $=$ strspn$($str$,$ str$2)$;

n $+=$ strcspn$($str$,$ str$2)$;

n $+=$ strnlen$($str$,2)$;

printf$("\%$i$",$ n$)$;

return $0$;

$\}$

Given the code above, what's the output if we run the program prog with the command $"./$prog $47747"$