#include <iostream>
#include <string>
using namespace std;

int main(){
    string buf;
    cin >> buf;
    int sum = 0;
    int p = 0;
    while(1){
      if (buf[p] == '\0'){
        break;
      }
      sum += buf[p]- '0';
      p++;
    }
    cout << sum << endl;
}