#include "bits/stdc++.h"
using namespace std;

#define REP(i, n) for(int i=0; i<(n); i++)

int N,T;
string s;
signed main()
{
    cin >> s;
    int cnt = 0;
    REP(i,s.size()) {
        cnt += atoi(s.substr(i,1).c_str());
    }
    cout << cnt << endl;
    return 0;
}