using System;
using System.Linq;
using System.Collections.Generic;

namespace Contest
{
    class Program
    {
        static void Main(string[] args)
        {
            AGC025.A();
        }

        class AGC025
        {
            public static void A()
            {
                var N = Read.Int();
                int sum = 0;
                while (N > 0)
                {
                    sum += N % 10;
                    N /= 10;
                }
                Console.WriteLine(sum == 1 ? 10 : sum);
            }
            public static void B()
            {
                var N = Read.Int();
                var A = Read.Long();
                var B = Read.Long();
                var K = Read.Long();

                var comb = Util.Combin(N + 1, Util.P);
                MOD sum = 0;
                for(int i = 0; i <= N; ++i)
                {
                    if ((K - i * A) % B == 0)
                    {
                        var j = (K - i * A) / B;
                        if (j < 0 || j>N) { continue; }
                        sum += comb(N, i) * comb(N, (int)j);
                    }
                }
                Console.WriteLine(sum.V);
            }
            public static void C()
            {
                var N = Read.Int();
                var LR = Read.TupleInt(N);
                var La = Enumerable.Range(0, N).OrderBy(i => -LR[i].Item1).ToArray();
                var Ra = Enumerable.Range(0, N).OrderBy(i => LR[i].Item2).ToArray();

                Func<int[], int[], List<int>> gen = (a1, a2) =>
                  {
                      List<int> list = new List<int>();
                      int idx1 = 0,idx2 = 0;
                      HashSet<int> hash = new HashSet<int>();
                      while (true)
                      {
                          while (hash.Contains(a1[idx1])) { idx1++; }
                          list.Add(a1[idx1]); hash.Add(a1[idx1]);
                          if (list.Count == N) { break; }
                          while (hash.Contains(a2[idx2])) { idx2++; }
                          list.Add(a2[idx2]); hash.Add(a2[idx2]);
                          if (list.Count == N) { break; }
                      }
                      return list;
                  };
                Func<List<int>, long> calc = (a) =>
                {
                    long total = 0;
                    int current = 0;
                    for(int i = 0; i < N; ++i)
                    {
                        var L = LR[a[i]].Item1;
                        var R = LR[a[i]].Item2;
                        if (current < L)
                        {
                            total += L - current;
                            current = L;
                        }
                        if (current > R)
                        {
                            total += current - R;
                            current = R;
                        }
                    }
                    total += Math.Abs(current);
                    return total;
                };
                Console.WriteLine(Math.Max(calc(gen(La, Ra)), calc(gen(Ra, La))));
            }
        }


        class Util
        {
            public static readonly long P = 998244353;
            public static long Inverse(long a, long p)
            {
                long b = p, c = 1, d = 0, e = 0, f = 0;
                while (b != 0)
                {
                    e = a / b;
                    f = b; b = a - e * b; a = f;
                    f = d; d = c - e * d; c = f;
                }
                c %= p;
                return c + (c < 0 ? p : 0);
            }
            public static long[] Facts(int n, long p)
            {
                var facts = new long[n + 1];
                facts[0] = 1;
                for (int i = 1; i <= n; ++i)
                {
                    facts[i] = (i * facts[i - 1]) % p;
                }
                return facts;
            }
            public static Func<int, int, long> Combin(int n, long P)
            {
                var fact = Facts(n, P);
                var inv = fact.Select(x => Inverse(x, P)).ToArray();
                return (N, M) =>
                {
                    if (N < 0 || N < M || M < 0) { return 0; }
                    return (((fact[N] * inv[M]) % P) * inv[N - M]) % P;
                };
            }
            public static long Power(long a, long n, long p)
            {
                long res = 1;
                long mult = a;
                for (int i = 0; i < 40; ++i)
                {
                    if ((n & ((long)1 << i)) > 0)
                    {
                        res = (res * mult) % p;
                    }
                    mult = (mult * mult) % p;
                }
                return res;
            }
        }
        struct MOD
        {
            public static long P = 998244353;
            public readonly long V;

            public MOD(long a) { this.V = a; }
            public static implicit operator MOD(long a) { return new MOD(a); }
            public static MOD operator +(MOD a, MOD b) { return new MOD((a.V + b.V) % P); }
            public static MOD operator -(MOD a, MOD b) { return new MOD((a.V - b.V + P) % P); }
            public static MOD operator *(MOD a, MOD b) { return new MOD((a.V * b.V) % P); }
            public static MOD operator /(MOD a, MOD b) { return new MOD((a.V * b.Inverse().V) % P); }
            public MOD Inverse() { return Util.Inverse(V, P); }
            public MOD Power(long n) { return Util.Power(V, n, P); }
            public override string ToString() { return V.ToString(); }
        }


        static class Read
        {
            static Queue<string> queue = new Queue<string>();
            static void Enqueue() { var ss = Console.ReadLine().Split(' '); foreach (var s in ss) { queue.Enqueue(s); } }
            public static int Int() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt32(queue.Dequeue()); }
            public static long Long() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt64(queue.Dequeue()); }
            public static string Str() { if (queue.Count == 0) { Enqueue(); } return queue.Dequeue(); }
            public static int[] IntN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray(); }
            public static long[] LongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt64(s)).ToArray(); }
            public static string[] StrN() { return Console.ReadLine().Split(' '); }
            public static Tuple<int, int>[] TupleInt(int n) { List<Tuple<int, int>> list = new List<Tuple<int, int>>(); for (int i = 0; i < n; ++i) { var ab = Read.IntN(); list.Add(new Tuple<int, int>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<long, long>[] TupleLong(int n) { List<Tuple<long, long>> list = new List<Tuple<long, long>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<long, long>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<string, string>[] TupleStr(int n) { List<Tuple<string, string>> list = new List<Tuple<string, string>>(); for (int i = 0; i < n; ++i) { var ab = Read.StrN(); list.Add(new Tuple<string, string>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<double, double>[] TupleDouble(int n) { List<Tuple<double, double>> list = new List<Tuple<double, double>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<double, double>(ab[0], ab[1])); } return list.ToArray(); }
            public static long[,] LongMatrix(int r, int c)
            {
                var mat = new long[r, c];
                for (int i = 0; i < r; ++i)
                {
                    var x = Read.LongN();
                    for (int j = 0; j < c; ++j)
                    {
                        mat[i, j] = x[j];
                    }
                }
                return mat;
            }
            public static Dictionary<int, HashSet<int>> AdjacencyList(int N, int M)
            {
                Dictionary<int, HashSet<int>> dict = new Dictionary<int, HashSet<int>>();
                for (int i = 0; i <= N; ++i)
                {
                    dict.Add(i, new HashSet<int>());
                }
                for (int i = 0; i < M; ++i)
                {
                    var ab = Read.IntN();
                    dict[ab[0]].Add(ab[1]);
                    dict[ab[1]].Add(ab[0]);
                }
                return dict;
            }
            public static Dictionary<int, Dictionary<int, long>> AdjacencyListWithWeight(int N, int M)
            {
                Dictionary<int, Dictionary<int, long>> dict = new Dictionary<int, Dictionary<int, long>>();
                for (int i = 0; i <= N; ++i)
                {
                    dict.Add(i, new Dictionary<int, long>());
                }
                for (int i = 0; i < M; ++i)
                {
                    var ab = Read.IntN();
                    dict[ab[0]].Add(ab[1], ab[2]);
                    dict[ab[1]].Add(ab[0], ab[2]);
                }
                return dict;
            }
        }
    }
}


Measured memory_bytes: 13396