#include <bits/stdc++.h>
#define rep(i ,n) for(int i=0;i<(int)(n);++i)
#define repr(i ,n) for(int i=n;i>(int)(n);--i)
#define rep1(i ,n) for(int i=1;i<=(int)(n);++i)
#define ALL(a) a.begin(), a.end()
#define SORT(a) sort(ALL(a))
#define bit_check(bit, i) ((bit>>(i)) & 1)
using namespace std;
typedef long long int int64;
typedef unsigned long long uint64;
template<class T> using V = vector<T>;
using I = int;
using VI = V<I>;
const int INF = 2e9;

template <class T> inline bool chmin(T& a, T b){if(a>b){a=b; return true;} return false;}
template <class T> inline bool chmax(T& a, T b){if(a<b){a=b; return true;} return false;}

int main(){
    string s; cin >> s;
    int sum = 0;
    rep(i , s.size()){
        sum+=s[i]-48;
    }
    cout << sum << endl;
}