Ada is poor in math, but now she wants to join Now or Never for learning. In the interview she was given a problem for her to solve but she couldn't solve it. Since there is time for her results, so she wants help from you.She will be given a positive integer P. A function $F(x)$is defined such that it always gives sum of digits of $x$.  For example $F(341)=3+4+1=8, F(0)=0$.You have to find two integers $u,v$, such that $0<=u,v<=P$ and $u+v=P$ and also  is largest possible among all such pairs.

CONSTRAINTS:

1<=P<=10¹²

$0<=u,v<=P$

$u+v=P$

INPUT:  The only line of input contains an integer P

OUTPUT:   Print largest $F(u)+F(v)$ among all pairs of integers $u,v$

Example:    

1) Input- 35

   Output-17

2) Input-10000000000

    Output:91