#include <bits/stdc++.h>
#include <set>
#define rep(i,n) for (int i=1; i <= (n); ++i)
#define all(a) a.begin(), a.end()
using ll = long long;
using namespace std;
 
// ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }


// const double PI = acos(-1);


int main() {
  string s; cin >> s;
  int sum = 0;
  rep(i,s.size()) {
    int n = (s[i] -'0');
    sum += n;
  }
  cout << sum << endl;
  return 0;
}