#include <iostream>

using namespace std;

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

    int zbir_na_cifri = 0;

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

        zbir_na_cifri += cifra;
    }


    cout << zbir_na_cifri << endl;

    return 0;
}