#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iterator>
#include <bitset>
#include <unordered_set>
#include <unordered_map>
#include <fstream>
#include <iomanip>
#include <cassert>
using namespace std;
int main()
{
    string s;
    cin >> s;
    long long sum = 0;
    for (int i = 0; i < s.size(); i++)
    {
        sum += s[i] - '0';
    }
    cout << sum << endl;
}