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 (3.4.3) (judge verdict: Accepted)

N = input()
N = list(map(int, N))

if len(N) == 1:
    print(N[0])
else:
    if not all(map(lambda n: n == 9, N[1:])):
        for i in range(len(N)):
            if i == 0:
                N[i] -= 1
            else:
                N[i] = 9

    print(sum(N))