题解 | #密码截取#

def run(seq):
    res = []
    for i in range(1, len(seq)):
        tmp = 1
        tmp1 = seq[:i][::-1]
        tmp2 = seq[i:]
        l = min(i, len(seq)-i)
        if l > 0:
            for j in range(l):
                if tmp1[j] == tmp2[j]:
                    if 2*(j+1) > tmp:
                        tmp = 2*(j+1)
                else:
                    break
        tmp1 = seq[:i+1][::-1]
        tmp2 = seq[i:]
        l = min(i+1, len(seq)-i)
        if l > 0:
            for j in range(l):
                if tmp1[j] == tmp2[j]:
                    if 2*(j+1) -1 > tmp:
                        tmp = 2*(j+1)-1
                else:
                    break
        res.append(tmp)
    return max(res)

seq = input().strip()
print(run(seq))