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: [246.278, 103.84, 214.867, -73.466, 230.048, -72.322, 172.891, 212.306, -78.335, 122.406]
Example Output: 107.851

Example Input: [12.155, 204.528, 85.84, 66.186]
Example Output: 92.177

Example Input: [137.543, 163.833, -74.02, 89.643, -93.579, -5.901, 16.248, 147.883]
Example Output:
47.706