Implement a function that takes a Null-terminated string and converts the lowercase characters (a-z) to uppercase and convert the uppercase oanes (A-Z) to lower case. In null-terminated strings, end of the string is specified by a special null character (i.e., value of 0). Your function should ignore non-alphabetical characters. For example, L!A##b@@3 should be converted to laB.

#a0: input array #a1: output array change_case: