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: Wrong Answer)

import sys
N = list(input())
ans, count = 0, 0
num = len(N)

if len(N) == 1:
    print(int(N[0]))
    sys.exit()
    
for i in range(num):
    a = int(N[i])
    if a != 9 and count == 0:
        if i == 0:
            N[i] = str(a-1)
            ans += int(N[i])
        else:
            ans += 8
            N[i-1] = '8'
            N[i] = '9'
        count = 1
    elif a == 9:
        ans += a
    elif a != 9:
        if count == 0:
            ans += 8
            N[i-1] = '8'
            N[i] = '9'
            count = 1
        else:
            ans += 9
            N[i] = '9'
print(ans)