#include <iostream>

using namespace std;

int main() {
    std::ios_base::sync_with_stdio(false);

    size_t longestSeq = 0;
    size_t currSeq = 0;

    string str;
    cin >> str;

    size_t len = str.length ();

    for (size_t i = 0; i < len; i++) {
        if (str[i] == '0') {
            currSeq++;
        } else {
            if (currSeq > longestSeq) {
                longestSeq = currSeq;
            }
            currSeq = 0;
        }
    }

    cout << ((longestSeq + 1) / 2) << endl;

    return 0;
}