
import java.util.Arrays;
import java.util.Scanner;
public class FindParkingSpace {
public static void main(String[] args) {
Scanner sc =new Scanner(System.in);
int[] ints = Arrays.stream(sc.nextLine().split(",")).mapToInt(Integer::parseInt).toArray();
solve(ints);
}
private static void solve(int[] ints) {
int maxDistance = 0 ,lastIndex = -1;
for(int i=0;i<ints.length;i+=1){
if(ints[i]==1){
if(lastIndex==-1){
lastIndex=i;
maxDistance=i;
}else{
maxDistance = Math.max(maxDistance,(i-lastIndex)/2);
lastIndex=i;
}
}
}
System.out.println(Math.max(maxDistance, (ints.length - lastIndex - 1)));
}
}