Kth Missing Positive Number

Given an array arr of positive integers sorted in strictly increasing order, and an integer k, return the k-th positive integer that is missing from this array.

Examples

Example 1:

Input: arr = [2, 3, 4, 7, 11], k = 5

Output: 9

Explanation: The missing positives in order are: 1, 5, 6, 8, 9, 10... The 5th missing is 9.

Example 2:

Input: arr = [1, 2, 3, 4], k = 2

Output: 6

Explanation: The missing positives are: 5, 6, 7... The 2nd missing is 6.

Example 3:

Input: arr = [1, 3], k = 1

Output: 2

Explanation: The first missing positive is 2.

Constraints

• 1 <= arr.length <= 1000
• 1 <= arr[i] <= 1000
• 1 <= k <= 1000
• arr[i] < arr[i+1]