#include <bits/stdc++.h>
using namespace std;

int main(){
    string veze;
    vector<long long> priestor;
    long long counter=0; 
    pair<long long, long long> mx = {0, 0};  // cislo index
    cin >> veze;

    if (veze.size() > 1){
        for (int i=1; i<veze.size(); i++){
            if (veze[i] == '0'){
                counter ++;
            }
            else if (veze[i] == '1' && veze[i-1] != '1'){
                priestor.push_back(counter);
                if (counter > mx.first){
                    mx.first = counter;
                    mx.second = priestor.size()-1;
                }
                counter = 0;
            }
        }
    }

    if (priestor.size() > 0){
        priestor[mx.second] = (priestor[mx.second]+1) / 2;
        mx.first = 0;

        for (int i=0; i<priestor.size(); i++){
            if (priestor[i] > mx.first) mx.first = priestor[i];
        }
        cout << mx.first << endl;
    }
    else{
        cout << 0 << endl;
    }
}