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=int(N)
N3=[int(x) for x in list(N)]
#n=int(N)
if n<10:
    print(n)
    exit()
else:
    ans=sum(N3)
    for i in range(len(N)-1):
        N2=int(N[:i+1])-1
        
        N1=[int(x) for x in list(str(N2))]
        ans=max(ans,sum(N1)+9*(len(N)-i-1))
    print(ans)