#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;

    int zbir_na_cifri = 0;
    for(int i = n; i > 0; i /= 10) {
        int cifra = i % 10;

        zbir_na_cifri += cifra;
    }

    cout << zbir_na_cifri << endl;
    return 0;
}