A $$k$$-universal circular string is a circular string that contains every possible $$k$$-mer constructed over a given alphabet.

Assignment

Write a function universal_circular_string that takes an integer $$k \in \mathbb{N}_0$$. The function must return a $$k$$-universal circular string. If multiple such strings exist, the function may return any one.

Example

>>> universal_circular_string(4)
'0111101100101000'
>>> universal_circular_string(5)
'01111101110011010110001010010000'