Sum of Missing Numbers

Create a function that returns the sum of missing numbers from the given list.

Examples

sum_missing_numbers([4, 3, 8, 1, 2]) ➞ 18
# 5 + 6 + 7 = 18

sum_missing_numbers([17, 16, 15, 10, 11, 12]) ➞ 27
# 13 + 14 = 27

sum_missing_numbers([1, 2, 3, 4, 5]) ➞ 0
# No Missing Numbers (i.e. all numbers in [1, 5] are present in the list)

Notes

The numerical range to consider when searching for the missing numbers in the list is the sequence of consecutive numbers between the minimum and maximum of the numbers (inclusive).