题解 | #最长回文子串#

import sys

sum1=0
sum2=0
list=[]
str1=input()
for i in range(len(str1)-1):
    if str1[i]==str1[i+1]:
        j=i
        k=i+1
        while j>-1 and k<len(str1) and str1[j]==str1[k]:
            j-=1
            k+=1
            sum2+=2
        list.append(sum2)
        sum2=0
    else:
        sum2 = 1
        j = i-1
        k = i + 1
        while j > -1 and k < len(str1) and str1[j] == str1[k]:
            j -= 1
            k += 1
            sum2 += 2
        list.append(sum2)
        sum2 = 0
sum1=max(list)
print(sum1)