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.

Example Input: [231.352, -24.17]
Example Output: 103.591

Example Input: [82.748, 43.804, -13.469, 226.705, -7.478]
Example Output: 66.462

Example Input: [229.99, -32.685, -4.59, -60.366, 217.034, -90.514]
Example Output:
43.145