题解 | #密码截取#

mima = str(input())
longest = 0
length = len(mima)

for j in range(0,length):
    count_1 = 0
    count_2 = 0
    while(j+count_1<length and j-count_1>=0 and mima[j-count_1] == mima[j+count_1]):
        count_1 += 1
    while(j+count_2+1<length and j-count_2>=0 and mima[j-count_2] == mima[j+count_2+1] ):
        count_2 += 1
    if(longest <= max((count_1*2-1),(count_2*2))):
        longest = max((count_1*2-1),(count_2*2))
print(longest)