#include <iostream>
#include <vector>
#include <string>

#define ull unsigned long long

using namespace std;

int countOnes(ull a) {
    int c = 0;
    for (int i = 0; i < 40; ++i) {
        if ((a & 1) == 1) {
            ++c;
        }
        a >>= 1;
    }
    return c;
}

int main()
{
    string s;
    cin >> s;
    if (s[0] == 0) {
        cout << "-1\n";
        return 0;
    }
    ull bitmask = ((ull)1 << s.length()) - 1;
    ull currentState = 0, bestState = 0;
    int ones = 0;
    for (int i = 0; i < s.length(); ++i) {
        currentState <<= 1;
        currentState |= (s[i] == '0' ? 0 : 1);
        ones += s[i] == '0' ? 0 : 1;
    }
    bestState = currentState;
    int iter = 0;
    for (int j = 0; j < 39 && currentState != bitmask; ++j) {
        for (int i = 1; i < 40; ++i) {
            ull st = (currentState | (currentState >> i));
            int z = countOnes(st);
            if (z > ones) {
                bestState = st;
                ones = z;
            }
        }
        currentState = bestState;
        ++iter;
    }
    cout << iter << endl;
    return 0;
}