def cock(s):
    smart_len=0
    for j in range(len(s)):
        start=j
        cock_string = ''
        for i in range(start,len(s)):
            cock_string+=s[i]
            if cock_string in s[i:start-1:-1]:
                if smart_len <= len(cock_string):
                    smart_len=len(cock_string)
                    print('start', start)
                    print('cock_string:',cock_string)
                    print(smart_len)
                    print(s[i:-start:-1])
                    print('-------')
    print(smart_len)


def main():
    s='aa'
    print(s)
    cock(s)

if __name__ == "__main__":
    main()