#! /usr/bin/env python3


river = input()
forward = [0] * len(river)
backward = [0] * len(river)
counter = 0
for i in range(len(river)):
    if river[i] == '1':
        counter = 0
    forward[i] = counter
    counter += 1

for i in range(len(river) - 1, -1, -1):
    if river[i] == '1':
        counter = 0
    backward[i] = counter
    counter += 1


maxi = 0

for i in range(len(river)):
    mini = min(forward[i], backward[i])
    if maxi < mini:
        maxi = mini

print(maxi)