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 PyPy3 (2.4.0) (judge verdict: Wrong Answer)

n = input()

if len(n) == 1:
  print(n)
  exit()

ok = False
ans = ""
for i, c in enumerate(n):
  x = int(c)
  if x == 9:
    ans += "9"
  else:
    if ok:
      ans += "9"
    else:
      if i == len(n)-1:
        ans = ans[:-1]
        ans += str(int(n[i-1])-1)
        ans += "9"
      else:
        ans += str(x-1)
    ok = True
    
t = 0
for c in ans:
  x = int(c)
  t += x
print(t)