#include<string>
#include<iostream>

using namespace std;

int main()
{
    string s;
    cin >> s;
    int ans = 0;
    int cur = 0;
    for(int i = 0; i < s.size(); i++)
    {
        if(s[i] == '0')
            cur++;
        else
        {
            ans = max(ans, cur);
            cur = 0;
        }
    }
    cout << ans/2 + ans%2 << endl;
}