Definition: In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.
Input: [166.643, 246.788, -69.254, -10.306, -88.121, 24.476, -36.495, -64.252, 20.08]

21.062