Deepest Subarray

You are given an array which may contain subarrays. Your task is to find the depth of the deepest subarray.

• [a] = 1 depth
• [[a]] = 2 depth
• [[[a]]] = 3 depth, etc

Examples

deepest([1, [2, 3], 4, [5, 6]]) ➞ 2

deepest([[[[[[[[[[1]]]]]]]]]]) ➞ 10

deepest([1, 4, [1, 4, [1, 4, [1, 4, [5]]]]]) ➞ 5

Notes

N/A