题解 | #最长回文子串#

# left->  <-right
#     'abba'


def isPalindrome(s):
    left = 0
    right = len(s) - 1
    while left < right:
        if s[left] != s[right]:
            return False
        left += 1
        right -= 1
    return True


# print(isPalindrome('aba'))
# print(isPalindrome('abc'))
# print(isPalindrome('abba'))
s = input()
len_s = len(s)
max_substring = ""
# i    : 字符串左闭包
# j + 1: 字符串右开包
for i in range(0, len_s, 1):
    for j in range(i + 1, len_s, 1):
        if isPalindrome(s[i : j + 1]) and len(s[i : j + 1]) > len(max_substring):
            max_substring = s[i : j + 1]
# print(max_substring)
print(len(max_substring))