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: [103.885, 191.867, 82.228, 177.708, 136.093, -17.022]
Example Output: 112.46

Example Input: [162.26, 79.268]
Example Output: 120.764

Example Input: [100.154, 90.27, 1.618, 227.9, -46.241, 70.688]
Example Output:
74.065

