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 main() {
	var n int64
	fmt.Scan(&n)

	s := strconv.FormatInt(n, 10)
	all9 := true
	for _, c := range s {
		tmp, _ := strconv.Atoi(string(c))
		if tmp != 9 {
			all9 = false
		}
	}
	if all9 {
		fmt.Println(len(s) * 9)
		return
	}

	var first string
	first = string(s[0])
	f, _ := strconv.Atoi(first)
	count9 := len(s) - 1

	all9 = true
	for i := 1; i < len(s); i++ {
		tmp, _ := strconv.Atoi(string(s[i]))
		if tmp != 9 {
			all9 = false
		}
	}
	if all9 {
		fmt.Println(f + count9*9)
		return
	}

	ans := f - 1 + count9*9

	fmt.Println(ans)
}