De Bruijn Sequence

Your task is to construct a minimum-length bit string that contains all possible substrings of length n. For example, when n=2, the string 00110 is a valid solution, because its substrings of length 2 are 00, 01, 10 and 11. Input The only input line has an integer n. Output Print a minimum-length bit string that contains all substrings of length n. You can print any valid solution. Constraint