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: [126.453, 169.516, 109.837, 208.695, 113.906, 56.894, 171.345, 126.81]
Example Output: 135.432

Example Input: [-57.838, -63.616, 49.646, -45.262, 73.1, -82.399, 47.168]
Example Output: -11.314

Example Input: [-19.273, 114.945, -15.716, 108.77, -56.249, 159.262, 26.992, -43.847, 214.335]
Example Output:
54.358

