#include <bits/stdc++.h>

using namespace  std;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    char ch = 0;
    int count_of_zeros;
    int days = 0;
    int ret = EOF;
    while(ch != EOF && ch != '\n'){
        ch = (char)getchar();
        if( ch == '0'){
            count_of_zeros++;
        }
        else{
            days = max(days, (count_of_zeros+1) / 2);
            count_of_zeros = 0;
        }
    }
    cout << days << endl;
    return 0;
}