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 PyPy3 (2.4.0) (judge verdict: Accepted)

n = int(input())
s = str(n)
len_s = len(s)

dp = [[0]*(len_s+1) for i in range(2)]

dp[0][1] = int(s[0])
dp[1][1] = int(s[0]) - 1

for i in range(1, len_s):
    for num in range(int(s[i]) + 1):
        dp[0][i+1] = max(dp[0][i+1], dp[0][i] + num)
        
    for num in range(int(s[i])):
        dp[1][i+1] = max(dp[1][i+1], dp[0][i] + num)
    
    for num in range(10):
        dp[1][i+1] = max(dp[1][i+1], dp[1][i] + num)

print(max(dp[0][len_s], dp[1][len_s]))