#include <bits/stdc++.h>
#define int long long
using namespace std;

int ctoi(char c) {
  if( c >= '0' && c <= '9' ) return c-'0';
  else return -1;
}

signed main() {
  string S;
  cin >> S;
  int ans = 0;
  for( int i = 0; i < S.size(); i++ ) ans += ctoi(S.at(i));
  cout << ans << endl;
}