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: [-15.843, 236.17, -79.922, -29.879]
Example Output: 27.632

Example Input: [-27.872, -9.249, 218.646, -32.0, 49.715, 58.225, 118.489, 29.679, 31.407]
Example Output: 48.56

Example Input: [147.533, -75.226, 95.038, 210.463, 189.565, -0.611, 238.251, 77.388, 157.353, 136.831]
Example Output:
117.658