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 Lua (5.3.2) (judge verdict: Accepted)

n=io.read("*n")
o=tostring(n)
for i=2,#o do
    if o:sub(i,i)~="9" then
        print(math.floor(tonumber(o:sub(1,1)-1)+9*(#o-1)))
        return
    end
end
print(math.floor(tonumber(o:sub(1,1))+9*(#o-1)))