#include<iostream>
#include<algorithm>
#include<vector>
#include<cmath>
#include<cstdio>
#include<string>

using namespace std;
using ll = long long;

int main(){ 
        string str;
        int sum = 0;
        cin >> str;
        for(int i=0;i<str.size();i++){
                sum+=(str[i]-'0');
        }
        cout << sum;
        return 0;
}