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 = int(input())
A = []
while N != 0:
  A.append(N%10)
  N //= 10
n = len(A)
nine = 0
for i in range(n-1):
  if A[i] == 9:
    nine += 1
if nine == n - 1:
  print(sum(A))
else:
  for i in range(n-1):
      A[i] = 9
  if A[n-1] > 1:
    A[n-1] -= 1
    print(sum(A))
  else:
    print(sum(A[i] for i in range(n-1)))