Implement a function that performs a recursive merge sort. The function should be recursive and takes in an array of integers. The output should be an array with the input sorted in ascending order.

The input array may be empty and may contain negative or duplicate integers.

Examples

mergeSort([9, 3, 6, 2, 1, 11]); // [1, 2, 3, 6, 9, 11]
mergeSort([12, 16, 14, 1, 2, 3]); // [1, 2, 3, 12, 14, 16]