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 (3.4.3) (judge verdict: Accepted)

n = int(input())


def dsum(n):
    res = 0
    while n > 0:
        res += n % 10
        n //= 10
    return res


min_sum = float('inf')
for a in range(1, n):
    min_sum = min(min_sum, dsum(a) + dsum(n - a))
print(min_sum)