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: Wrong Answer)

N = int(input())

def digit_sum(X):
    s = 0
    while(X > 0):
        s += X % 10
        X = int(X / 10)
    return s

min_ = 10 ** 5
for A in range(N):
    B = N - A
    val = digit_sum(A) + digit_sum(B)
    min_ = min(min_, val)

print(min_)