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 Python (3.8.2) (judge verdict: Accepted)

n = list(input())
n = list(map(int,n))
m = len(n)
if m == 1:
    print(n[0])
elif len(set(n)) == 1 and n[0] == 9:
    print(9 * m)
elif len(set(n)) == 2 and n[0] != 9 and n[1] == 9:
    print(n[0] + (m - 1) * 9)
else:
    print(n[0] - 1 + (m - 1) * 9)