#include <iostream>
using namespace std;

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

    int i = n, cifra, zbir = 0;
    while(i > 0)
    {
        cifra = i % 10;
        i /= 10;
        zbir += cifra;
    }
    cout << zbir << endl;

    return 0;
}