题解 | #最长回文子串#

s = list(input())
list =[]
for i in range(len(s)-1):  #从1个数字开始向两边
    for j in range(len(s)-i-1):
        if s[i-j]== s[i+j]:
            list.append(2*j-1)
            continue
        else:
            break

    if s[i] == s[i+1]: #从2个相同的数字开始，向两边
        for j in range(len(s)-i-1):
            if s[i-j]== s[i+1+j]:
                #存放在列表里...
                list.append(2*j+2)
                continue
            else:
                break
print(max(list))