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: [229.28, 202.632, 129.717, 211.459, 203.204]
Example Output: 195.258

Example Input: [-17.026, 165.89]
Example Output: 74.432

Example Input: [183.153, -39.704, 219.913, -31.843, 176.247, 92.053, 2.707, -81.491]
Example Output:
65.129