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: Runtime Error)

import sys
input = sys.stdin.readline

# A - Digit Sum 2
def digit_sum(str_num):
	sum = 0	
	
	for i in range(len(str_num)):
		sum += int(str_num[i])
	
	return sum


N = input()
patterns = [N]

for i in range(len(N)-1):
	if N[i] != '0':
		left, right = '', ''  
				
		if i > 0:
			left = N[:i]
		
		n = int(N[i]) - 1
		
		if i < len(N) - 1:
			right = '9' * (len(N)-i-1) 
		
		patterns.append(left + str(n) + right)

ans = 0

for p in patterns:
	ans = max(ans, digit_sum(p))
	
print(ans)