#include <iostream>
#include <algorithm>
#include <vector>
#include <math.h>

using namespace std;

int main()
{
    int max_zeros = 0;
    char number;
    int cur_len = 0;
    while (cin >> number)
    {
        
        if (number == '0')
        {
            cur_len++;
        }
        else
        {
            cur_len = 0;
        }

        max_zeros = max_zeros > cur_len ? max_zeros : cur_len;
    }
    max_zeros = max_zeros / 2 + max_zeros % 2;

    cout << max_zeros << "\n";

    return 0;
}