What's the Length of the Missing Array?

Create a function that takes an array of arrays and return the length of the missing array.

Examples

findMissing([[1], [1, 2], [4, 5, 1, 1], [5, 6, 7, 8, 9]]) ➞ 3

findMissing([[5, 6, 7, 8, 9], [1, 2], [4, 5, 1, 1], [1]]) ➞ 3

findMissing([[4, 4, 4, 4], [1], [3, 3, 3]]) ➞ 2

Notes

• Test input arrays won't always be sorted in order of length.
• If the array of arrays is null or empty, your function should return false.
• If an array within the parent array is null or empty, return false.
• There will always be a missing element and its length will be between the given arrays.