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 Python (3.8.2) (judge verdict: Accepted)

import sys, math
from functools import lru_cache
sys.setrecursionlimit(500000)
MOD = 10**9+7

def input():
    return sys.stdin.readline()[:-1]

def mi():
    return map(int, input().split())

def ii():
    return int(input())

def i2(n):
    tmp = [list(mi()) for i in range(n)]
    return [list(i) for i in zip(*tmp)]


def main():
    N = ii()
    m = 10**100
    for i in range(1, N//2+1):
        A = i
        B = N-i
        Da = sum(int(a) for a in str(A))
        Db = sum(int(b) for b in str(B))
        m = min(m, Da+Db)
    print(m)


if __name__ == '__main__':
    main()