#include <iostream>
#include <vector>

using namespace std;

int getK(string input) {
    string copy;

    int maxK = 0;
    int maxMoved = 0;
    int len = input.size();

    int moved;

    for(int k = 1; k <= len; k++) {
        copy = input;
        moved = 0;

        for(int i = len-1; i >= 0; i--) {
            if(input[i] == '1' && i+k < len && input[i+k] == '0') {
                moved++;
            }
        }

        if(moved > maxMoved) {
            maxMoved = moved;
            maxK = k;
        }
    }

    return maxK;
}

int done(string& input) {
    for(int i = 0; i < input.size(); i++) {
        if(input[i] == '0') return 0;
    }
    return 1;
}

int main()
{
    string input;
    getline(std::cin, input);

    if(input[0] == '0') {
        cout << (-1) << endl;
        return 0;
    }

    int len = input.size();

    int rounds = 0;
    while(!done(input)) {
        int K = getK(input);

        //cout << "chose K: " << K << endl;

        for(int i = len-1; i >= 0; i--) {
            if(input[i] == '1') {
                if(i+K < len) {
                    input[i+K] = '1';
                }
            }
        }

        //cout << "updated input: " << input << endl;

        rounds++;
    }

    cout << rounds << endl;


    return 0;
}