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: Wrong Answer)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func read() string {
	sc.Scan()
	return sc.Text()
}

func main() {
	n, _ := strconv.Atoi(read())
	m, _ := strconv.Atoi(read())
	a, _ := strconv.Atoi(read())
	b, _ := strconv.Atoi(read())
	nm := n * m
	if nm%2 == 1 || nm < 2*(a+b) {
		fmt.Println("NO")
	}
	if n < 1 && b > 0 {
		fmt.Println("NO")
	}
	if m < 1 && a > 0 {
		fmt.Println("NO")
	}

}