题解 | #密码截取#

a=input()
la=len(a)
li=[]
i=0
while i < la:#单核
    j=0
    while 1:
        if i-j<0 or i+j>la-1:
            j-=1
            break
        elif a[i-j]==a[i+j]:
            j+=1
        else:
            j-=1
            break
    li.append(j*2+1)
    i+=1
i=0
while i < la:#偶核
    j=0
    while 1:
        if i-j<0 or i+j+1>la-1:
            j-=1
            break
        elif a[i-j]==a[i+1+j]:
            j+=1
        else:
            j-=1
            break
    li[i]=max(j*2+2,li[i])
    i+=1
print(max(li))