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: [128.152, 95.16, 70.113, -16.853]
Example Output: 69.143

Example Input: [-30.66, 134.777, 39.637, -41.053, 60.502, -99.875, -32.055, 51.52, 216.645, 11.994]
Example Output: 31.143

Example Input: [83.07, -0.908, 204.987, 135.371]
Example Output:
105.63