Two strings of equal length can be interlaced like the teeth of a zipper to form a new word. For example, interlacing cota and rain yields croatian. The following class constructs a ZipperWord from two strings.
Your task is to complete the implementation of the toStringHelper method below. That method computes the zipped word resulting from interleaving characters from first and second, starting with the given position. Interleave the characters at that position and combine with a recursive call to toStringHelper.