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

int main() {
  string C;
  cin >> C;
  int ans = C.size() - 1;
  for (int i = 0; i < C.size(); ++i) {
    if (C[i] == '0') {
      --ans;
    }
  }
  cout << ans << endl;
}