You are given a string `num`

, representing a large integer. Return *the largest-valued odd integer (as a string) that is a non-empty substring of *

`num`

`""`

A **substring** is a contiguous sequence of characters within a string.

**Example 1:**

Input:num = "52"Output:"5"Explanation:The only non-empty substrings are "5", "2", and "52". "5" is the only odd number.

**Example 2:**

Input:num = "4206"Output:""Explanation:There are no odd numbers in "4206".

**Example 3:**

Input:num = "35427"Output:"35427"Explanation:"35427" is already an odd number.

**Constraints:**

`1 <= num.length <= 10`

^{5}`num`

only consists of digits and does not contain any leading zeros.

class Solution {
public String largestOddNumber(String num) {
}
}