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 digit
	implicit none
    character(len=17) :: n
    character(len=17),parameter :: q = '99999999999999999'
    integer :: j
    integer :: i, ans
    
    read(*,*) n
    read(n(1:1),*) j !最高位の数字
    
    i = len_trim(n) !桁数

    if ( i==1 ) then
    	write(*,*) n
        stop
    end if
    
    if ( n(2:i) == q(2:i) ) then
    	ans = 9*(i-1) + j        
        write (*,*) ans
        stop
    end if
    
    ans = 9*(i-1) + j - 1
    write(*,*) ans
    stop
end program digit