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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define PI 3.1415926535897932384626433
#define mod 1000000007

int gcd(int a, int b) { return b ? gcd(b, a%b) : a; }

int lcm(int a, int b) { return a * b / gcd(a, b); }

int main(){
    ll n;
    cin >> n;
    if(n % 10 == 0){
        cout << 10 << endl;
        return 0;
    }
    int ans = 0;
    while(n > 0){
        ans += n % 10;
        n /= 10;
    }
    cout << ans << endl;
    return 0;
}