#include <bits/stdc++.h>
#define pb push_back
#define FOR(i, a, b) for(int i = a; i < b; i++)
//#define FOR(i, a) FOR(i, 0, a)
#define st first
#define nd second
//#pragma GCC optimize ("Ofast")
//#pragma GCC target("sse, sse2, sse3, sse4, popcnt, abm, mmx, avx, time=native")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;

int main() {
	ios_base::sync_with_stdio(0);
	string s;
	cin>>s;
	
	int n = s.length();
	int res = 0;
	//cout<<s<<" "<<n<<" "<<(1<<3)<<endl;
	
	if(s[0] == '0') {
		res = -1;
	} else {
		
		int zero = 0;
		while(true) {	
			//cout<<s<<endl;
			zero = -1;
			FOR(i, 0, n) {
				if(s[i] == '0') {
					zero = i;
					break;
				}
			}
			//cout<<" "<<zero<<endl;
		
			if(zero == -1)
				break;
			else {
				for(int i=n-1; i>=0; i--) {
					if( i + zero < n && s[i] == '1' )
						s[i+zero] = '1';
				}
			}
			//cout<<s<<" "<<zero<<endl;
			res++;
		}
	}
	cout<<res<<endl;
	
	return 0;
}