//
// Created by cteam24 on 11/27/21.
//
#include <iostream>

int main(void) {

    int maxZeroStreak = 0;
    int currentZeroStreak = 0;
    char c;

    while(scanf("%c", &c) && c != '\n') {
        if(c == '0')
            currentZeroStreak += 1;
        else if(c == '1') {
            if(currentZeroStreak > maxZeroStreak)
                maxZeroStreak = currentZeroStreak;
            currentZeroStreak = 0;
        }
    }

    printf("%d\n", (maxZeroStreak + 1 ) / 2 );

    return 0;
}