题解 | #密码截取#

def longest(left,right,myster):
    while left>=0 and right<len(myster) and myster[left]==myster[right]:
        left-=1
        right+=1
    return myster[left+1:right]
mystr=input()
res=""
for i in range(len(mystr)):
    cnt1=longest(i,i,mystr)
    cnt2=longest(i,i+1,mystr)
    cur=cnt1 if len(cnt1)>len(cnt2) else cnt2
    if len(cur)>len(res):
        res=cur
print(len(res))