695 B | 695 chars
import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
s = input()
s_1 = s[0] == '1'
l = []
crt = ans = 0
for i in s:
if i == '1':
if crt > 0:
if not s_1:
ans = max(ans, crt)
else:
ans = max(ans, (crt + 1) // 2)
crt = 0
continue
if i == '0':
crt += 1
if crt > 0:
ans = max(ans, crt)
p(ans)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
d = solve()