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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"fmt"
	"strconv"
)

func max(x, y int) int {
	if x > y {
		return x
	}
	return y
}

func main() {
	var n int
	fmt.Scan(&n)

	s := strconv.Itoa(n)
	c, _ := strconv.Atoi(string(s[0]))
	for i := 1; i < len(s); i++ {
		if s[i] != '9' {
			fmt.Println(c - 1 + (len(s)-1)*9)
			return
		}
	}
	fmt.Println(c + (len(s)-1)*9)
}