output_description: Print the minimum possible value of "the sum of the digits of A" plus "the sum
  of the digits of B".
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
attempt: # coding: utf-8
  import re
  import math
  import itertools
  from copy import deepcopy
  import fractions
  import random
  from heapq import heappop, heappush
  import time
  import os
  import sys
  import datetime
  from functools import lru_cache
  
  readline = sys.stdin.readline
  sys.setrecursionlimit(2000)
  # import numpy as np
  alphabet = "abcdefghijklmnopqrstuvwxyz"
  mod = int(10**9 + 7)
  inf = int(10**20)
  
  
  def yn(b):
      if b:
          print("yes")
      else:
          print("no")
  
  
  def Yn(b):
      if b:
          print("Yes")
      else:
          print("No")
  
  
  def YN(b):
      if b:
          print("YES")
      else:
          print("NO")
  
  
  class union_find:
      def __init__(self, n):
          self.n = n
          self.P = [a for a in range(N)]
          self.rank = [0] * n
  
      def find(self, x):
          if x != self.P[x]:
              self.P[x] = self.find(self.P[x])
          return self.P[x]
  
      def same(self, x, y):
          return self.find(x) == self.find(y)
  
      def link(self, x, y):
          if self.rank[x] < self.rank[y]:
              self.P[x] = y
          elif self.rank[y] < self.rank[x]:
              self.P[y] = x
          else:
              self.P[x] = y
              self.rank[y] += 1
  
      def unite(self, x, y):
          self.link(self.find(x), self.find(y))
  
      def size(self):
          S = set()
          for a in range(self.n):
              S.add(self.find(a))
          return len(S)
  
  
  def is_power(a, b):  # aはbの累乗数か
      now = b
      while now < a:
          now *= b
      if now == a:
          return True
      else:
          return False
  
  
  def bin_(num, size):
      A = [0] * size
      for a in range(size):
          if (num >> (size - a - 1)) & 1 == 1:
              A[a] = 1
          else:
              A[a] = 0
      return A
  
  
  def fac_list(n, mod_=0):
      A = [1] * (n + 1)
      for a in range(2, len(A)):
          A[a] = A[a - 1] * a
          if mod > 0:
              A[a] %= mod_
      return A
  
  
  def comb(n, r, mod, fac):
      if n - r < 0:
          return 0
      return (fac[n] * pow(fac[n - r], mod - 2, mod) * pow(fac[r], mod - 2, mod)) % mod
  
  
  def next_comb(num, size):
      x = num & (-num)
      y = num + x
      z = num & (~y)
      z //= x
      z = z >> 1
      num = y | z
      if num >= (1 << size):
          return False
      else:
          return num
  
  
  def get_primes(n, type="int"):
      A = [True] * (n + 1)
      A[0] = False
      A[1] = False
      for a in range(2, n + 1):
          if A[a]:
              for b in range(a * 2, n + 1, a):
                  A[b] = False
      if type == "bool":
          return A
      B = []
      for a in range(n + 1):
          if A[a]:
              B.append(a)
      return B
  
  
  def is_prime(num):
      if num <= 2:
          return False
      i = 2
      while i * i <= num:
          if num % i == 0:
              return False
          i += 1
      return True
  
  
  def join(A, c=" "):
      n = len(A)
      A = list(map(str, A))
      s = ""
      for a in range(n):
          s += A[a]
          if a < n - 1:
              s += c
      return s
  
  
  #############################################
  n = int(input())
  if is_power(n, 10):
      print(10)
  else:
      n = str(n)
      n = list(n)
      n = list(map(int, n))
      print(sum(n))
  
problem_description: 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).
samples: [{"input": "15", "output": "6\n    \n\nWhen A=2 and B=13, the sums of their digits are 2 and 4, which minimizes the\nvalue in question.\n\n* * *"}, {"input": "100000", "output": "10"}]