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 (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

var (
	rdr   = bufio.NewReaderSize(os.Stdin, 1000000)
	reply string
)

func main() {
	var ans int
	n := atoi(nextSlice())
	for _, a := range n {
		ans += a
	}
	if ans == 1 {
		ans *= 10
	}
	fmt.Println(ans)
}

func readLine() string {
	buf := make([]byte, 0, 1000000)
	for {
		l, p, e := rdr.ReadLine()
		if e != nil {
			panic(e)
		}
		buf = append(buf, l...)
		if !p {
			break
		}
	}
	return string(buf)
}

func nextSlice() []string {
	return strings.Split(readLine(), "")
}

func atoi(a []string) (b []int) {
	b = make([]int, len(a))
	for i := range a {
		b[i], _ = strconv.Atoi(a[i])
	}
	return
}

func atof(a []string) (b []float64) {
	b = make([]float64, len(a))
	for i := range a {
		b[i], _ = strconv.ParseFloat(a[i], 64)
	}
	return
}

func scanSlice2(n int) (a []int, b []int) {
	a = make([]int, n)
	b = make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&a[i], &b[i])
	}
	return
}

func scanFloatSlice2(n int) (a []float64, b []float64) {
	a = make([]float64, n)
	b = make([]float64, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&a[i], &b[i])
	}
	return
}

// ---------------------------------------------------

func abs(a int) int {
	if a > 0 {
		return a
	}
	return -a
}

func gcd(a, b int) int {
	if b == 0 {
		return a
	}
	return gcd(b, a%b)
}

func min(a ...int) int {
	min := a[0]
	for i := 1; i < len(a); i++ {
		if min > a[i] {
			min = a[i]
		}
	}
	return min
}

func max(a ...int) int {
	max := a[0]
	for i := 1; i < len(a); i++ {
		if max < a[i] {
			max = a[i]
		}
	}
	return max
}

func sum(a []int) (ans int) {
	for i := range a {
		ans += a[i]
	}
	return
}

// ---------------------------------------------------

func yesOrNo(b bool) {
	if b {
		reply = "Yes"
		fmt.Println(reply)
		return
	}
	reply = "No"
	fmt.Println(reply)
}

func yesorNO(b bool) {
	if b {
		reply = "YES"
		fmt.Println(reply)
		return
	}
	reply = "NO"
	fmt.Println(reply)
}