Problem:
Score : 200 points

Problem Statement

Takahashi has two positive integers A and B.

It is known that A plus B equals N.
Find the minimum possible value of "the sum of the digits of A" plus "the sum of the digits of B" (in base 10).

Constraints

2 ≤ N ≤ 10^5

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the minimum possible value of "the sum of the digits of A" plus "the sum of the digits of B".

Sample Input 1

15

Sample Output 1

6

When A=2 and B=13, the sums of their digits are 2 and 4, which minimizes the value in question.

Sample Input 2

100000

Sample Output 2

10

Solution in Go (1.6) (judge verdict: Accepted)

package main

import (
	"fmt"
	"math"
)

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

	min := math.MaxInt64
	for i := 1; i < n; i++ {
		a := i
		b := n - a
		sum := sumDigit(a) + sumDigit(b)
		if sum < min {
			min = sum
		}
	}

	fmt.Println(min)
}

func sumDigit(n int) int {
	sum := 0
	for n > 0 {
		sum += n % 10
		n /= 10
	}
	return sum
}