题解 | #密码截取#

import sys

line = input().strip()
ctlist = []
len1 = len(line)
resault = 0
for i in range(len1):
    k, j, lenABA = i - 1, i + 1, 1
    while k >= 0 and j <= len1-1:
        if line[k] == line[j]:
            k, j, lenABA = k - 1, j + 1, lenABA + 2
        else:
            break
    k, j, lenABBA = i, i + 1, 0
    while k >= 0 and j <= len1-1:
        if line[k] == line[j]:
            k, j, lenABBA = k - 1, j + 1, lenABBA + 2
        else:
            break
    re = max(lenABA,lenABBA)
    resault = max(resault,re)
print(resault)