#include<bits/stdc++.h>
#define rep(i, x) for(ll i = 0; i < x; i++)
#define rep2(i, x) for(ll i = 1; i <= x; i++)
#define all(a) (a).begin(),(a).end()
using ll = long long;
using ld = long double;
using namespace std;
signed main() {
	string s; cin >> s; ll n = s.size() - 1;
	rep2(i, s.size() - 1) { if (s[i] == '0') { n--; } }
	cout << n << endl;
	return 0;
}