#include <iostream>
#include <vector>
#include <climits>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <bitset>
#include <utility>
#include <numeric>
#include <queue>
#include <stack>

using ll = long long;
using namespace std;

constexpr int MOD = 1e9 + 7;
constexpr ll MOD_LL = ll(1e9) + 7;

int main(void) {
	string c;
	cin >> c;
	
	int n = (int)c.size() - 1;
	int m = n;
	for(int i = 0; i < (int)c.size(); ++i) {
		if( c[i] == '0' ) m--;
	}
	
	cout << min(n, m) << endl;
	
	return 0;
}