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)

N = int(input())

ret = 0
f = 0
for idx,c in enumerate(str(N)):
    tmp = int(c)
    if f == 1:
        ret += 9
        continue
    if tmp != 9 and idx == 0:
        ret += tmp-1
        f = 1
        continue
    elif tmp != 9:
        ret -= 1
        f = 1
        ret += 9
        continue
    else:
        ret += 9
        continue
print(ret)