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())
l = len(n)

for i in range(l):
    n[i] = int(n[i])

score = 0

if l == 1:
    print(n[0])
else:
    if n.count(9) == l:
        score = sum(n)
    elif n.count(9) == l-1:
        if n[0] != 9:
            score += sum(n)
        else:
            score += 8 + 9*(l-1)
    else:
        if n[0] != 9:
            score += n[0]-1 + 9*(l-1)
        else:
            for j in range(l):
                if n[j] != 9:
                    n[j-1] = 8
                    score += 8 + 9*(l-1)
                    break
    print(score)