题解 | #最长回文子串#

string = input().strip()

max_len = 0

for i in range(0, len(string)):
    left = i - 1
    right = i + 1
    len_ABA = 1
    while left >=0 and right <= len(string) - 1:
        if string[left] == string[right]:
            len_ABA += 2
            left -= 1
            right += 1 
        else:
            break
    
    left = i
    right = i + 1
    len_ABBA = 0

    while left >= 0 and right <= len(string) - 1:
        if string[left] == string[right]:
            len_ABBA += 2
            left -= 1
            right += 1
        else:
            break
    max_len = max([max_len, len_ABA, len_ABBA])

print(max_len)