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: Wrong Answer)

def main():
    N = list(str(input()))
    if len(N) == 1:
        print(N)
    else:
        if all(n == "9" for n in N[1:]):
            print(int(N[0])+9*(len(N)-1))
        else:
            print((int(N[0])-1)+9*(len(N)-1))

if __name__ == "__main__":
    main()