#include <iostream>
#include <bitset>
#include <string>

using namespace std;

int main(){
	string s;
	cin >> s;

	const int sz = s.length();
	string pr(sz,'1');

	bitset<40> b1(s);
	bitset<40> b2(s);
	bitset<40> pare(pr);

	if(s[0] == '0'){
		cout << -1 << endl;
	}
	else{
		int res = 0;
		int l1 = sz - 1;
		
		while(b1 != pare){
			for(int i=l1;i>=0;i--){
				if(!b1[i]){
					l1 = i;
					break;
				}
			}
			
			res+=1;

			int l = sz-1-l1;

			b1 >>= l;
			b1 |= b2;
			
			b2 = b1;
			//cout << b1.to_string() << endl;
		}
		cout << res << endl;
	}

	return 0;
}