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 (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <math.h>

int main(void){
	int N;
	int A=0,B=0,ans=0;
	scanf("%d",&N);
	int sw;
	int n;
	int i = 0;
	int x = N;
	while(x > 9){
		x = x/10;
		i++;
	}// N = 10^i + x
	int a=i;A=1;
	for(i=0;i<a;i++){
		A = A*10;
		if(A==N) A=A/10;
	}
	B = N-A;
	ans = 1;//A
	int b=B;
	int c=B;
	while(b>9){
		i=0;
		while(b>9){
			b = b/10;
			i++;
		}
		ans+=b;
//		printf("%d\n",ans);
		c = c-b*pow(10,i);
		b=c;
		if(c==0){break;}
	}
	if(c != 0){	ans+=c;	}
	
	printf("%d",ans);
	return 0;
}