#include <stdio.h>

int main() {
	int max_zeros = 0;
	int cur_zeros = 0;
	char read = '1';
	while (1) {
		scanf("%c", &read);
		if(read == '1') {
			max_zeros = max_zeros > cur_zeros ? max_zeros : cur_zeros;
			cur_zeros = 0;
		}
		else if (read == '0') {
			cur_zeros++;
		}
		else break;
	}
	printf("%d", (max_zeros+1)>>1);
	return 0;
}