给你一个由字母组成的字符串，创建一个新字符串，其中每个字母都是原始字符串中距离该字母最近的元音字母。如果该字母就是元音字母，则将其复制到新字符串中。 


"whatsup"
The resulting string would be "auiuup" for the input string "whatsup", where each non-vowel letter is replaced by its nearest vowel in the original string.