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 Fortran (GNU Fortran 9.2.1) (judge verdict: Accepted)

program prob4
    implicit none
    integer(8) :: N
    integer :: m

    read(*,*) N
    N = N + 1

    m = 0
    do while(N >= 10)
        N = N / 10
        m = m + 1
    end do

    write(*,*) 9*m + N - 1

    stop
contains
end program prob4