Re$-$code the following portion of main$()$ so that it accepts a single command$-$line parameter that identifies the external file name of the file being opened, instead of the constant string that's currently being passed in$.$ In addition, add error checking using try$/$throw$/$catch to ensure that the user typed exactly two command$-$line parameters $($this includes the program name and the file name$).$ That is$,$ convert the following fragment to use command$-$line parameters to open a file, with error checking. If there's an error, exit$(0)$;$.$

int main$()\{$

ifstream infile;

infile.open$("$scores$.$txt$")$;