#include <bits/stdc++.h>

using namespace std;

#define F first 
#define S second
#define ER erase
#define IS insert
#define PI acos(-1)
#define PB pop_back
#define MP make_pair
#define MT make_tuple
#define LB lower_bound
#define UB upper_bound
#define EB emplace_back
#define lowbit(x) (x & -x)
#define SZ(x) ((int)x.size())
#define ALL(x) x.begin(), x.end()
#define RALL(x) x.rbegin(), x.rend()
#define SOS ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);cout<<fixed<<setprecision(10)

typedef long long LL;
typedef vector<LL> VL;
typedef vector<int> VI;
typedef vector<bool> VB;
typedef pair<LL, LL> PLL;
typedef vector<string> VS;
typedef vector<double> VD;
typedef pair<int, int> PII;
typedef unsigned long long ULL;
typedef pair<double, double> PDD;
typedef tuple<int, int, int> TIII;
typedef vector<pair<LL, LL> > VPLL;
typedef vector<pair<int, int> > VPII;

template <typename A> using VE = vector<A>;
template <typename A> using USET = unordered_set<A>;
template <typename A> using HEAP = priority_queue<A>;
template <typename A, typename B> using PA = pair<A, B>;
template <typename A, typename B> using UMAP = unordered_map<A, B>;
template <typename A> using RHEAP = priority_queue<A, vector<A>, greater<A> >;

template <typename A> A MAX(const A &a) { return a; }
template <typename A> A MIN(const A &a) { return a; }
template <typename A> A MAX(const A *a, const A *b) { return *max_element(a, b); }
template <typename A> A MIN(const A *a, const A *b) { return *min_element(a, b); }
template <typename A, typename... B> A MAX(const A &a, const B&... b) { return max(a, MAX(b...)); }
template <typename A, typename... B> A MIN(const A &a, const B&... b) { return min(a, MIN(b...)); }
template <typename A, typename B = typename std::iterator_traits<A>::value_type> B MAX(A a, A b) { return *max_element(a, b); }
template <typename A, typename B = typename std::iterator_traits<A>::value_type> B MIN(A a, A b) { return *min_element(a, b); }

int main(){
    SOS;
    string s;
    cin>>s;
    int size=s.size();
    int ans=0;
    for(int i=0;i<size;++i){
        ans+=s[i]-'0';
    }
    cout<<ans<<'\n';
}