Create a function that can nest a flat list to represent an incremental depth level sequence.

Examples

incremental_depth([1, 2]) ➞ [1, [2]]

incremental_depth([1, 2, 3, 4, 5]) ➞ [1, [2, [3, [4, [5]]]]]

incremental_depth([1, 3, 2, 6]) ➞ [1, [3, [2, [6]]]]

incremental_depth(["dog", "cat", "cow"]) ➞ ["dog", ["cat", ["cow"]]]

Notes

• The elements do not matter to the function, you should increment by index.
• Expect the array length to be from 2-20.