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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
class Program{
static void Main(string[] args){
var N = int.Parse(Console.ReadLine());
var min = 9999999;
for(int i=1;i<N-1;i++){
var A = i;
var B = N-i;
while(A > 10){
A = CalcDigitSum(A);
}
while(B > 10){
B = CalcDigitSum(B);
}
if(A + B < min){
min = A + B;
}
}
Console.WriteLine(min);
}
static int CalcDigitSum(int num){
var txt = num.ToString();
var res = 0;
foreach(char c in txt){
res += int.Parse(c.ToString());
}
return res;
}
}