You are given a positive integer n.
Return the maximum product of any two digits in n.
Note: You may use the same digit twice if it appears more than once in n.
Example 1:
Input: n = 31
Output: 3
Explanation:
n are [3, 1].3 * 1 = 3.Example 2:
Input: n = 22
Output: 4
Explanation:
n are [2, 2].2 * 2 = 4.Example 3:
Input: n = 124
Output: 8
Explanation:
n are [1, 2, 4].1 * 2 = 2, 1 * 4 = 4, 2 * 4 = 8.
Constraints:
10 <= n <= 109