题解 | #密码截取#

n = input().strip() 
def palindrome(s, left, right): 
    while left >= 0 and right len(s) and s[left] == s[right]:
        left -= 1  
        right += 1  
    return s[left + 1:right]
res = "" 
for i in range(len(n)):
    s1 = palindrome(n, i, i)
    s2 = palindrome(n, i, i + 1)
    res = s1 if len(res) len(s1) else res
    res = s2 if len(res) len(s2) else res 
print(len(res))