Given a non-negative integer N, find the largest number that is less than or equal to N with monotone increasing digits. (Recall that an integer has monotone increasing digits if and only if each pair of adjacent digits x and y satisfy x <= y.) Example 1: Input: N = 10 Output: 9 Example 2: Input: N = 1234 Output: 1234 Example 3: Input: N = 332 Output: 299 Note: N is an integer in the range [0, 10^9].