#include 

using namespace std;

int main()
{ 
    int n;
    cin >> n;
    
    int zbir =0 ;
    for(int x = n; x > 0; x /= 10) {
        int cifra = x % 10;
        zbir += cifra;
    }
    cout << zbir << endl;
   
    return 0;
}