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)

def digit_sum(x):
  if x < 10:
    return x
  return x % 10 + digit_sum(int(x / 10))
N = int(input())
ans = N
for i in range(1, int(N / 2) + 1):
  d = digit_sum(i) + digit_sum(N - i)
  if d < ans:
    ans = d
print(ans)