#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;
using namespace atcoder;

const int INF = 1e9;
const long long LINF = 1e18;

const int dx[] = {1,0,-1,0};
const int dy[] = {0,1,0,-1};

#define ll long long
#define uint unsigned int
#define ull unsigned long long
#define vint vector<int>
#define vll vector<long long>
#define pint pair<int,int>
#define pb push_back
#define mp make_pair
#define elif else if

#define sum(...) accumulate(ALL(__VA_ARGS__),0LL)
#define REP1(i,n) for (int i = 0; i < (n); i++)
#define REP2(i,a,b) for (int i = (a); i < (b); i++)
#define REP3(i,a,b,c) for (int i = (a); i < (b); i += (c))
#define LREP(i,a,b) for (ll i = (a); i < (b); i++)
#define DREP(i,n) for (int i = n - 1; i--;)
#define drep(i,cc,n) for (int i = (cc); i <= (n); i++)
#define rep(i,n) drep(i,0,n-1)
#define sz(s) (int)(s.size())
#define EACH(x,a) for (auto& (x) : (a))
#define ENDL cout << endl;
#define ALL(x) (x).begin(),(x).end()
#define RALL(x) (x).rbegin(),(x).rend()
#define YES(n) cout << ((n) ? "YES" : "NO" ) << endl;
#define yes(n) cout << ((n) ? "Yes" : "No" ) << endl;
#define INT(...) int __VA_ARGS__; input(__VA_ARGS__)
#define LL(...) long long __VA_ARGS__; input(__VA_ARGS__)
#define STR(...) string __VA_ARGS__; input(__VA_ARGS__)
#define ULL(...) unsigned long long __VA_ARGS__; input(__VA_ARGS__)
#define CH(...) char __VA_ARGS__; input(__VA_ARGS__)
#define DB(...) double __VA_ARGS__; input(__VA_ARGS__)
#define VINT(name, n) vector<int> name; input_array(n, name)
#define VLL(name, n) vector<long long> name; input_array(n, name)
#define VST(name, n) vector<string> name; input_array(n,name)
#define overload3(a,b,c,d,e, ...) e
#define REP(...) overload3(__VA_ARGS__, REP3,REP2,REP1)(__VA_ARGS__)
#define init_1(x) memset(x,-1,sizeof (x))
#define init0(x) memset(x,0,sizeof (x))
#define init1(x) memset(x,1,sizeof (x))

inline void out() { putchar(' '); }
inline void out(const bool &a) { printf("%d\n",a); }
inline void out(const int &a) { printf("%d\n",a); }
inline void out(const long long &a) { printf("%lld\n",a); }
inline void out(const unsigned long long &a) { printf("%llu\n",a); }
inline void out(const char &a) { printf("%c\n",a); }
inline void out(const char a[]) { printf("%s\n",a); }
inline void out(const float &a) { printf("%.10f\n",a); }
inline void out(const double &a) { printf("%.10f\n",a); }
inline void out(const long double &a) { printf("%.10Lf\n", a); }

// debug
/* #define _GLIBCXX_DEBUG */
void debug_out() { cout << endl; }

template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cout << H << " ";
  debug_out(T...);
}

#ifdef _DEBUG
#define debug(...) debug_out(__VA_ARGS__);
#else
#define debug(...)
#endif

template<class T> bool chmin(T& a, const T& b) {
  return b<a?a=b, 1:0;
}

template<class T> bool chmax(T& a, const T& b) {
  return b>a?a=b, 1:0;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p)
{
  os << "(" << p.first << "," << p.second << ")";
  return os;
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p)
{
  is >> p.first >> p.second;
  return is;
}

template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v)
{
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != (int)v.size() ? " " : "");
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, const vector<vector<T>> &v)
{
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << endl;
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, const vector<vector<vector<T>>> &v)
{
  for (int i = 0; i < (int)v.size(); i++) {
    os << "i = " << i << endl;
    os << v[i];
  }
  return os;
}

template <typename T>
istream &operator>>(istream &is, vector<T> &v)
{
    for (T &in : v)
        is >> in;
    return is;
}

template <typename T, typename S>
ostream &operator<<(ostream &os, const map<T, S> &mp)
{
  for (auto &[key, val] : mp) {
    os << key << ":" << val << " ";
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, const set<T> &st)
{
  auto itr = st.begin();
  for (int i = 0; i < (int)st.size(); i++) {
    os << *itr << (i + 1 != (int)st.size() ? " " : "");
    itr++;
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, const multiset<T> &st)
{
  auto itr = st.begin();
  for (int i = 0; i < (int)st.size(); i++) {
    os << *itr << (i + 1 != (int)st.size() ? " " : "");
    itr++;
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, queue<T> q)
{
  while (q.size()) {
    os << q.front() << " ";
    q.pop();
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, deque<T> q)
{
  while (q.size()) {
    os << q.front() << " ";
    q.pop_front();
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, stack<T> st)
{
  while (st.size()) {
    os << st.top() << " ";
    st.pop();
  }
  return os;
}

template <class T, class Container, class Compare>
ostream &operator<<(ostream &os, priority_queue<T, Container, Compare> pq)
{
  while (pq.size()) {
    os << pq.top() << " ";
    pq.pop();
  }
  return os;
}

using mint = modint998244353;
//* using mint = modint1000000007;

ostream &operator<<(ostream &os, const mint &i)
{
  os << i.val();
  return os;
}

ostream &operator<<(ostream &os, const vector<mint> &v)
{
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i].val() << (i + 1 != (int)v.size() ? " " : "");
  }
  return os;
}

template <class... T>
constexpr auto min(T... a) {
  return min(initializer_list<common_type_t<T...>>{a...});
}

template<class... T>
void input(T&... a) {
  (cin >> ... >> a);
}

template<typename T>
void input_array(const int n, vector<T>& vec) {
  vec.resize(n);
  for (T& x : vec) {
    cin >> x;
  }
}

void print() {
  cout << '\n';
}

template <typename T, class... Ts>
void print(const T& a, const Ts&... b) {
  cout << a;
  (cout << ... << (cout << ' ', b));
  cout << '\n';
}

int solve(string s) {
  int sum = 0;
  REP(i,sz(s)) {
    int a = s[i] - '0';
    sum += a;
  }
  return sum;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  STR(s);
  print(solve(s));
  return 0;
}