题解 | #密码截取#

my_str = input()
out = 0

for i in range(len(my_str)):
    len_ABA = 1
    k = i - 1
    j = i + 1
    while k >= 0 and j < len(my_str):
        if my_str[k] == my_str[j]:
            k -= 1
            j += 1
            len_ABA += 2
        else:
            break

    len_ABBA = 0
    k = i 
    j = i + 1   
    while k >= 0 and j < len(my_str):
        if my_str[k] == my_str[j]:
            k -= 1
            j += 1
            len_ABBA += 2
        else:
            break
    now_len = max(len_ABA,len_ABBA)
    if out < now_len:
        out = now_len
print(out)