Problem:
Score : 300 points

Problem Statement

Find the maximum possible sum of the digits (in base 10) of a positive integer not greater than N.

Constraints

1\leq N \leq 10^{16}

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the maximum possible sum of the digits (in base 10) of a positive integer not greater than N.

Sample Input 1

100

Sample Output 1

18

For example, the sum of the digits in 99 is 18, which turns out to be the maximum value.

Sample Input 2

9995

Sample Output 2

35

For example, the sum of the digits in 9989 is 35, which turns out to be the maximum value.

Sample Input 3

3141592653589793

Sample Output 3

137

Solution in Perl (v5.18.2) (judge verdict: Accepted)

#!/usr/bin/perl

( my $n = <STDIN> ) =~ s/[\x00-\x20]+$//io;

if( length($n) > 1 and $n !~ /^\d9+$/o ){
  $n =~ /^\d/;
  my $d1 = $&;
  my $d2 = $';
  $n = ( $d1 - 1 ) . ('9' x length($d2));
}
my @a = split('',$n);
my $tot = 0;
$tot += $_ foreach @a;
print "$tot\n";

exit(0);