def kaibun_parse(str,l)
    str1 = str[0..l-1]
    l.times{|i|
        tmp = str1[i..l-1]
        if tmp == tmp.reverse && tmp != str 
            return tmp
        end
    }
end

def kaibun_max(str,n)
    if n == 0
        return ""
    else
        tmp = [kaibun_max(str,n-1),kaibun_parse(str,n)]
        return tmp.max{|a,b|a.size <=> b.size}
    end
end

s = gets.chomp
puts kaibun_max(s,s.size).size