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: Accepted)

n = int(input())

def get_first(n):
	return int(str(n)[0])

def check(n):
	# x99..99かどうか
	s = str(n)
	for i in range(1, len(str(n))):
		if str(s[i]) != '9':
			return False
	return True

if check(n):
	res = get_first(n) + 9 * (len(str(n)) - 1)
else:
	res = (get_first(n) - 1) + 9 * (len(str(n)) - 1)

print(res)