#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
#endif

typedef unsigned int uint;
typedef long long int ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

#define loop while(1)
#define rep(i,n) for(ll i=0ll;(i)<(n);(i)++)
#define REP(i,a,n) for(ll i=(a);(i)<(n);(i)++)
#define FOR(i, a, b) for(ll i = a; i < (ll)(b); i++)
#define rrep(i,n) for(ll i=(n)-1;(i)>=(0ll);(i)--)
#define RREP(i,a,n) for(ll i=(n)-1;(i)>=(a);(i)--)
#define modi(a,b) (a%b+b)%b
#define sz(a) (int)(a).size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define foa(i,v) for(auto& (i) : (v)
#define bs(A,x) binary_search(all(A),x)
#define lb(A,x) (ll)(lower_bound(all(A),x)-A.begin())
#define ub(A,x) (ll)(upper_bound(all(A),x)-A.begin())
#define cou(A,x) (ll)(upper_bound(all(A),x)-lower_bound(all(A),x)))
#define el '\n'
#define spa " "
#define Yes cout << "Yes" << el
#define No cout << "No" << el
#define YES cout << "YES" << el
#define NO cout << "NO" << el
#define debug(x) cerr << #x << " = " << x << el
#define dout()  cout << fixed << setprecision(20)

const int inf = 1073741823;
const ll infl = 1LL << 60;
const string ABC = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const string abc = "abcdefghijklmnopqrstuvwxyz";
const long long mod99 = 998244353;
const long long mod107 = 1000000007;
const long long mod = mod99;

// 配列の要素を空白区切りで出力 第二引数をtrueにすると改行区切り
template<typename T> inline void print_vec(const vector<T> &v, bool split_line=false) {
    if(v.empty()){
        cout << "This vector is empty." << el;
        return;
    }
    constexpr bool isValue = is_integral<T>::value;
    for (int i = 0; i < (int)v.size(); i++) {
        if constexpr(isValue){
            if((v[i]==inf) || (v[i]==infl)) cout << 'x' << " \n"[split_line || i+1==(int)v.size()];
            else cout << v[i] << " \n"[split_line || i+1==(int)v.size()];
        }else cout << v[i] << " \n"[split_line || i+1==(int)v.size()];
    }
}

template<typename T1, typename T2> inline void print_vec(const vector<pair<T1,T2>> &v, bool split_line=false){
    if(v.empty()){
        cout << "This vector is empty." << el;
        return;
    }
    for(int i = 0; i < (int)v.size(); i++){
        cout << '{';
        auto [a,b] = v[i];
        constexpr pair<bool,bool> isValue = {is_integral<T1>::value, is_integral<T2>::value};
        if constexpr(isValue.first){
            if(a==inf || a==infl) cout << "x,";
            else cout << a << ",";
        }else cout << a << ",";
        if constexpr(isValue.second){
            if(b==inf || b==infl) cout << "x,";
            else cout << b;
        }else cout << b;
        cout << "}" << " \n"[split_line || i+1==(int)v.size()];
    }
}

template<typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
    bool compare = a < b;
    if(compare) a = b;
    return compare;
}
template<typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
    bool compare = a > b;
    if(compare) a = b;
    return compare;
}

// std::chronoを利用した時間計測用クラス
class Timer{
    chrono::system_clock::time_point start;
    public:
        Timer() : start(chrono::system_clock::now()) {}
    
        double count(){
            chrono::duration<double> Time_ = chrono::system_clock::now() - start;
            return Time_.count();
        }

        bool is_under(double x){
            return (this -> count()) < x;
        }
};

// std::uniform_int_distributionを利用した一様乱数生成クラス
class Random_Gen{
    random_device seed_gen;
    mt19937 engine;
    uniform_int_distribution<int64_t> dist;
    public:
        // Constructor [l,r]で生成する値の範囲を指定
        Random_Gen() : engine(seed_gen()) {}
        Random_Gen(int64_t l, int64_t r) : engine(seed_gen()), dist(l,r) {}
        
        // 現在の生成する値の範囲をstd::pairで返す
        pair<int64_t,int64_t> get_range(){
            return make_pair(dist.min(),dist.max());
        }
        // 生成する値の範囲を[l,r]に変更する
        void set_range(int64_t l, int64_t r){
            uniform_int_distribution<int64_t>::param_type Param(l,r);
            dist.param(Param);
        }
        // [l,r]内の一様分布の整数を返す
        int64_t gen(){
            return dist(engine);
        }
        int64_t operator()(){ return gen(); }
};


ll calc(ll n) {
    ll res = 0;
    while (n > 0) {
        res += n % 10;
        n /= 10;
    }
    return res;
}

int main() {
    ll S;
    cin >> S;

    ll res = calc(S);
    cout << res << endl;
}