import sys

s = input()
n = len(s)
res = 0
for i in range(n+1):
    for j in range(i,n+1):
        temp = s[i:j]
        if temp == temp[::-1]:
            res = max(res,len(temp))
print(res)

字符串的range+切片 要考虑长度+1的问题

因为 sss

0 1 2

是[:3]