#if !__INCLUDE_LEVEL__
#include __FILE__
using namespace std;

int main()
{
    string s;
    cin >> s;
    int ans=0;

    for(char c : s){
        ans += int(c-'0');
    }
    cout << ans << endl;
}

#else
#include <bits/stdc++.h>
#include <boost/format.hpp>
#include <boost/range/algorithm.hpp>
#define REP_(i, a_, b_, a, b, ...) for (int i = (a), lim##i = (b); i < lim##i; i++)
#define REP(i, ...) REP_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define ALL(v) (v).begin(),(v).end()
template <class T> bool chmin(T &a, const T &b) { return a > b ? a = b, true : false; }
template <class T> bool chmax(T &a, const T &b) { return a < b ? a = b, true : false; }
template <class T> using V = std::vector<T>;
#endif