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>
#pragma GCC optimize("unroll-loops,no-stack-protector")
#pragma GCC target("sse,sse2,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define watch(x) cout << (#x) << " is " << (x) << endl

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;

const int MOD = 1e9 + 7;

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n; cin >> n;
    int best = INT_MAX;
    if(n == 2)
    {
        cout << 2;
        return 0;
    }
    for(int i = 1; i < n/2; i++)
    {
        int cnt = 0;
        int a = i;
        int b = n - i;
        while(a > 0)
        {
            cnt += a % 10;
            a /= 10;
        }
        while(b > 0)
        {
            cnt += b % 10;
            b /= 10;
        }
        best = min(best, cnt);
    }
    cout << best;

    return 0;
}